But heartache was bearing down anyway. As Brown recounts in her new book, After Cleo Came Jonah, her teenage daughter Lydia was vanishing into the most mystic extremes of Buddhism.
It was a stand-off. Whenever Brown tried to discuss Lydia's faith and future, her daughter retreated into silence and Brown, who found it hard to bite her tongue, was terrified she would completely alienate her.
And then the crisis with Lydia accelerated. Brown, diagnosed with advanced breast cancer, had to have an urgent mastectomy. Instead of staying to support her mother, the implacable Lydia flew off to study to be a nun at a remote monastery in Sri Lanka, a country torn by terrorism.
"You can't go. I forbid it!" cried Brown. "The tickets are booked and paid for," said Lydia coldly, an almost exact echo of a conversation between Brown and her own mother many years before, when Brown flew off to Britain at age 18 to get married.
Losing Sam and slowly coming to terms with that trauma, then the struggle years later with Lydia, "was another form of grief at the time and I overreacted", says Brown on the phone from Melbourne. "I proved myself quite a hypocrite really because I'd raised her and all the kids [Rob, Lydia and Katharine, the daughter she had with second husband Philip] to be very open spiritually. But that was just one step too far.
"I used to run through the scenarios at night - she's not pregnant, she's not on drugs, she hadn't even got a tattoo. If you are looking for a way to rebel against your parents, she had to turn over a lot of stones to find an area that was going to upset me. I analysed the mistakes I'd made in my own life and they were almost all to do with poor education and low self-esteem. So I thought with my own two daughters I would really work on those - and it all backfired."
Just before the operation, Brown wrote down a list of things that made her angry and decided she needed a friend who "didn't continually twist the subject around to their own problems".
"I smiled when I read my list of friend requirements," she writes in the book. "Understanding on that level was almost beyond human. It sounded more like a cat."
After the operation, Brown awoke in a haze and thought she saw Lydia sitting by the window. A wishful hallucination, surely? But her daughter had come back - Brown later discovered the monk who led the monastery paid Lydia's fares to fly to Melbourne as soon as he found out she was ill - and the pair grew much closer as Brown slowly recuperated.
With her daughter at home (temporarily) and her health on the mend, there was still something missing in the big old Prahran house named "Shirley". Brown's sister Mary, visiting from New Plymouth, told her about "the cutest Siamese kitten in a pet shop across town". Brown, still in a lot of pain and quite sure she'd be able to resist any feline overtures, decided to go to have a look, as an "outing", complete with drainage bottle.
Only one kitten in the shop was awake, quickly scaling the inside of the large cage to reach eye-level with Brown. "The kitten suddenly froze and, spread-eagled against the wire, fixed me with a sapphire gaze ... I couldn't look away. We were caught in a mutual stare."
She was snared. But the kitten (Tonkinese, it turned out) she took home and named Jonah was both a darling and a disaster. He was a snuggler when it suited him - but he was also a plate-smasher, nervy, needy, an escape artist and, as he grew older, a stinking sprayer. When the spraying began, Philip was all for sending Jonah to "the farm", a suggestion that made Brown feel "cold for the first time" towards her husband.
Luckily for the cat, a daily dose of a form of Prozac stopped the spraying and, says Brown, Jonah, now aged 4, "has become a much more pleasant individual, very charming as long as he has his half-pill a day. He just adores attention - he loves it when photographers come to the house and he'll pose endlessly".
Photographers have become increasingly frequent visitors to Brown's home since Cleo came out and sales spread across Britain, Europe and the United States. The book, Brown notes wryly, had to become a global success before the Australians "really sat up and noticed".
"And that's fine, because I like living a quiet life but now we are getting literary tours, with people driving past the house and going to Spoonful [her local cafe] to try out the coffee. It's surreal. We might have to move."
Brown's success at this stage of her life - she is 58 - is a vindication, given her confidence as a writer was rock-bottom when she started work on the book. "I had an identity crisis when we moved to Melbourne," says the former Auckland Star, Next magazine and provincial New Zealand newspaper columnist. "We moved because of Philip's job and I just assumed I'd be able to slip into another journalism job but I had so much going on. Rob got terribly ill [with a colon disease], the girls found it really traumatic trying to fit into their school, Philip was working 14-hour days and I was terribly homesick. I think I was a bit down really.
"I kept the syndicated column going, which was great because it kept me in touch with those readers, especially in provincial New Zealand. Then, when I started that book no publisher would touch it. I couldn't even find an agent, so my profile slipped below the radar.
"Maybe everyone was right and I had forgotten how to write, because occasionally I'd get fired by provincial editors who'd tell me my writing was stale and I started to believe he was right - and it was always a he. So I went off to a weekend writing course and was in awe of the talent of the other people and that's where I found out about the Friday Pitch."
Friday Pitch, Allen & Unwin's initiative to help writers get a short synopsis and first chapter read by publishers, was Brown's way in. When Cleo was released in 2009, it immediately became a hit at the London Book Fair, with her publisher telling her "this will change her life". It has - and Philip's life as well.
"Some people say it's very threatening for a man to have a successful wife but he has always been very low-key. But in Portugal I felt so sorry for him. About 18 months ago, a national newspaper came to interview me and I asked him to come along. The photographer was lining me up against the wall and he said to Philip, 'Sir, would you move out of the way, please?'"
The books, Brown believes, have been successful (at time of writing After Cleo: Came Jonah was number two on New Zealand's international adult non-fiction best-seller list) because they provide hope.
"I think when you have a tragedy, at the time you think what good can come from this? It's the end of my life, the end of everything. The first hint of it was when I lost Sam and the first letters came in from other grieving parents, which were so valuable for me. You get to the point when you have done most of your grieving and you can transform that into something useful - I think that is why I wrote Cleo.
"In a similar way, those struggles you have with your kids when they are in their teens or 20s, they can be absolutely decimating. There were times when I thought I'd lost Lydia forever and that she'd gone into a sect. That was another form of grief at the time."
Brown's life will change and expand again when the movie, still in the very early stages of pre-production with Fiona Samuels working on the script, comes out. Who will play her? Brown offers a very knowing laugh. "They have given me hints - it's pretty much a megastar."
But, as fans of the book will know, the more important question should be: who will play Cleo?
After Cleo Came Jonah (Allen & Unwin $35) is out now.
Helen Brown will tour New Zealand this month, appearing in seven centres from May 24 to 30.
For tour dates and times see: helenbrown.com.au/nz-tour.htm
