The language was such that one has to wonder if, even allowing for her obvious grief, Kim, 61, had rather taken leave of her senses.
Clearly she felt blind fury that Sarah Jessica, 52 — known to all as SJP — was, in her view, yet again fostering her public image as a 'nice girl' offering support to her "friend Kim" — and that muscling in on the Cattrall family's grief was a step too far.
No one who has followed the relationship between the women was under the illusion it was very good — they are both known to have diva-ish tendencies and have been feuding on and off for years.
But until this weekend the depth of hostility involved, on Cattrall's part at least, was unknown. It would seem the huge resentment she appears to feel towards SJP — over her status on the show, her salary and her influence — boiled over in that one, vitriolic rant.
So is SJP entirely innocent or does Kim have grounds for her anger?
Certainly there were times when the "mean girls" atmosphere on Sex And The City reached such a pitch that neither Queen Bee SJP nor the other two stars, Cynthia Nixon and Kristin Davis, would speak to Kim.
Not a word — beyond what the scripts demanded — despite 15-hour days filming together, for months on end.
The three women would eat lunch apart from Kim, too, according to sources on set. When they were shooting out of town, they would stay in different hotels. There was no girly exchange of gossip while they were all having their make-up done.
The reasons were many; over the years arguments raged over everything from status and money to the amount of nudity in love scenes. SJP got to keep her bra on, which rankled with Kim who, as sexually voracious Samantha Jones, was required to bare all at every opportunity.
But essentially, it all boiled down to which actress was the bigger star.
SJP, nominally the star of the show as sex columnist Carrie Bradshaw — and incidentally best friends with series producer Michael Patrick King — fought hard against Cattrall's natural scene-stealing charisma.
SJP got pay rises, promotion to executive editor and ever more say over the series, which ran between 1998-2004. Kim, however, did not — despite her furious protests.
Evidently matters became so unpleasant that Kim decided she was done with Sex And The City, and despite two successful spin-off films, she turned her back on a third. That prompted some semi-public sniping in October last year after Kim appeared on a British chat show — but that was all. Which is what makes Kim's outbursts this weekend all the more jaw-dropping.
"It has always been a contentious relationship — they were the two alpha dogs on set and it was uncomfortable from day one," says a source close to the show. "As time went on, SJP definitely looked down on Kim for her sexpot image and her third divorce."
Sex And The City, based on the book by Candace Bushnell, was a huge, era-defining success for the cable network HBO. Within a few seasons, the four stars of the show were among the biggest names in television. And no one's name was bigger than SJP's.
She and Cynthia Nixon (Miranda) had known each other for years, and she quickly became fast friends with Kristin Davis (Charlotte), too.
Kim's only ally was Darren Starr, who had created the show and produced it. But after the second season he was replaced by Michael Patrick King, a close friend of SJP's.
By 2002, SJP had negotiated an "executive producer" credit to reflect her importance and was reputedly being paid nearly three times as much as her co-stars — $1 million per episode compared with $350,000.
But there was more to it than just the money.
A source says: "From the point when SJP had her executive producer credit, she took ownership of the show and this always grated on Kim. Kim wanted an executive producer credit from series three but was never given one.
"She felt SJP got more screen time than she did, which was only fair because Sarah Jessica was the lead, but it caused tension. Then she had to watch while SJP was given a say on the lines her character said, plot lines and so on. And SJP never had to show nudity, whereas Kim had to be naked the whole time."
The source adds that the clash of the egos made life on set awkward. "SJP and the other girls . . . called each other and socialised and Kim was always the one left out."
Then in 2002, a showbiz magazine claimed Kim had let slip that Cynthia Nixon had suffered a miscarriage and was planning another pregancy. Nixon was said to be stunned by the 'betrayal' and the repercussions rumbled on for a long time.
A crew member reportedly said: "Sarah, Kristin and Cynthia have frozen Kim out. They won't sit with her for meals, there's no going out after the show for a nightcap. It's so bad she basically sits in her dressing room alone — sometimes crying."
It was around this time, while on location in Atlantic City, that SJP reportedly rented a house for herself, Kristin and Cynthia, leaving Kim on her own.
When this came to light, the series' maker HBO had to to play down talk of divisions — after all this was a show that was heavily sold as a joyous exploration of the sustaining power of female friendships.
According to a spokesman, Kim stayed in a different house "because she was married and her husband was supposed to come down".
It is telling, however, that when the TV series ended in 2004, SJP reportedly broke down in tears while filming the last episode but Kim was rather more brusque.
"If I miss them, I can just put on a DVD, like everyone else," she said.
She later told chat show host Jonathan Ross that she had felt "after six years it was time for all of us to participate in the financial windfall of Sex And The City. When they didn't seem keen on that, I thought it was time to move on."
Ironically, the chance to cash in came as soon as the last episode had been transmitted — as fans clamoured for a film.
Released in 2008 — the highest grossing romantic comedy of the year, taking $400 million worldwide — the movie had been preceded by a long delay due to salary negotiations: more specifically to Kim Cattrall saying "No".
Later, she said she was going through a divorce and caring for her sick father, and simply felt too exhausted to contemplate a return.
Whatever the truth, the result of the negotiations was that SJP was paid more than £10 million, Kim Cattrall around £5 million and Cynthia Nixon and Kristin Davis around £2 million each.
Great efforts were made all round to foster solidarity, and in December 2009 Cattrall turned up to support SJP on the red carpet premiere of her film Did You Hear About The Morgans?
SJP told Elle magazine that she "adored" Kim Cattrall, and said: "I wouldn't have done the movie without her."
Sadly, it seems that this may have been the high water mark in their association, because the making of Sex And The City 2 broke the peace between them once and for all.
SJP admitted filming had led to conflicts. "You're on set, you're working 90-hour weeks, you're never home, you're exhausted," she said. "Sometimes feelings get hurt. But I don't have any regrets about how I've treated people."
One flashpoint this time around was the confidentiality agreement the film company made everyone sign. Under its terms, anyone proved to be the leak of the story about the movie was liable to pay up to $2.5 million in damages.
Kim Cattrall nearly came a cropper after she was photographed holding a script with some of the dialogue visible. Bosses issued a warning telling her to be more careful. "I thought: 'You have got to be kidding!'" she said later.
"This isn't state secrets, it's the f***ing script for a movie!" Warring egos also made themselves felt on the second film. Even Chris Noth, who played Carrie's enduring love Mr Big, joined in. He felt the biggest ego on set belonged to Cattrall.
"All actresses have someone working for them called a 'vanity person'", he said. "Their job is to make sure you look good at all times during filming. Most actors only have one person doing this job. But on Sex And The City, all of the stars had two. Except Kim, who had three."
During the making of the film on location in Morocco, Cattrall stayed at the Royal Mansour hotel, while the other three were living at La Mamounia.
There was no let up in tension after the film was released to widespread criticism. The script was deemed to be too heavy on puns and SJP's fondness for this type of joke was blamed.
Outwardly there were denials, of course, that relations had descended again into the deep freeze. Indeed, Cattrall told this newspaper in 2010: "I think Sarah is fantastic. She is a born leader and she guides the crew and cast in such a strong but gentle way."
But clearly, she was sick of deferring to the "born leader", whatever the financial rewards, because negotiations to bring Cattrall back into the fold for a third movie came to naught.
A script was written in 2013 and negotiations opened in 2016. But last year it was reported that Cattrall had "killed" the film with "outrageous demands", refusing to be in it unless Warner Bros agreed to produce other films which she had in development.
This she denied, saying: "The only demand I ever made was that I didn't want to do a third film . . . and that was back in 2016." SJP confirmed rather more diplomatically: "It's over. We're not doing it. I'm disappointed."
The implication was that she was not to blame. However, Cattrall was having none of it.
In a TV interview with Piers Morgan, she explained: "The common ground we had was the series and the series is over. For me it's over; it's over with no regrets. I just wish that Sarah had been nicer."
And that, of course, is the theme she returned to this weekend in her furious social media post. There are few in Hollywood who would bet on a rapprochment any time soon.
