"Just like that," says Witherspoon, who has notched up 19.5 million followers on Instagram. "Fifteen years ago [our image] was prescribed by a journalist. Now we have the chance to be in control of our own narrative."
"That is appealing," says Aniston. "I've got to get on social media."
Few people in the modern era have been subject to more conjecture than Aniston. Ever since she played Rachel Green on Friends, she has had a claim to be one of the most famous actresses on the planet (she and Witherspoon are reportedly being paid around US$1.25 million ($1.98 million) each per episode for The Morning Show).
Her marriages – to Brad Pitt and Justin Theroux – and her so-called "failure" to procreate have been the subject of endless magazine articles.
It makes The Morning Show all the more surprising because the character she plays is a TV show host called Alex Levy, who an all-male executive team has decreed "past her prime".
"I wanted to feel vulnerable," says Aniston. "I wanted to show the raw, the messy, the unflattering. This is a woman holding it together. One of the challenges for [my] character is the trauma and turmoil going on in her private life, and the toll that that takes on her emotionally, physically, mentally, versus the character that she is when she has to get up, put on a face and smile to America."
Alex Levy's battle with a persona she has maintained for 15 years is, Aniston says, very personal. There are countless scenes in the first few episodes of The Morning Show in which she's necking Red Bull and coffee, or holding back tears, and then she walks past a poster of her own gleaming smile. The gap between perception and reality comes crashing home.
"I can relate to that," Aniston says. "Of course there are times when you don't want anyone to see you, or you don't want to be photographed or even go out of the house. Nothing is as it seems in a glossy magazine."
The Morning Show, on which Aniston is also an executive producer, seems to have been expressly designed to put her through the wringer. Her character is assailed by corporate ageism, the alpha-male executives want her out and, to cap it all, her partner on TV, Mitch (Steve Carell), has been sacked for sexual misconduct.
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This storyline, Aniston says, was a late addition to the series.
"The show existed before MeToo," says Aniston. "It was going to be pulling back the curtain on the New York media world and looking behind the scenes of the morning talk shows. But once MeToo happened, the conversation changed drastically.
"Then we just incorporated it into the script, and sat and thought about what the tone would be. We wanted it to be raw and honest and vulnerable – it looks at the grey areas surrounding MeToo. It's not black and white."
Without giving too much away, those "grey areas" include Carell's disgraced co-host Mitch and the trouble some men of his era have had in the MeToo era to even understand what they have done wrong.
"He's just a charming narcissist who believes that everybody wants to sleep with him, not understanding that there's a power dynamic that he's abusing," says Aniston.
I put it to Aniston and Witherspoon that the show might strike more of a chord with an American audience than a British one that is less familiar with institutions like NBC's Today and ABC's Good Morning America.
"I don't think you have to know much about American TV breakfast news to get something out of this show," says Witherspoon. "The people in this show all come from different backgrounds, have different levels of success and they're all highly motivated, but they're working at cross purposes, so when they collide it's fascinating. If you've ever worked with or for someone in a pressured environment, you'll know what we're about."
Witherspoon plays Bradley Jackson, a Southern reporter transported into the top tier of television news after a clip of her rebuking an ignorant protester at a pro-coal march goes viral. Suddenly, she finds herself in conflict with Aniston's Alex, a woman-to-woman rivalry that offsets The Morning Show's critique of corporate patriarchy.
"Someone put it to me a couple of weeks ago," says Witherspoon, "that their relationship is not Thelma and Louise but it's not All About Eve. So what is it? They asked."
This got Witherspoon's back up. "I was like, 'Do you know there are thousands of different relationships that women have with each other. And this is just one of those."
I make the mistake of calling Alex and Bradley's competition "catfighting". Witherspoons responds: "If it was a scene with two guys, would it be called catfighting? To me, it's two human beings who are having a conflict about a very specific thing, which is their work."
There is an irony underlying the entire show, which is that broadcast television's problems and declining influence are largely due to the rise and rise of big tech – companies such as Facebook, Google and, of course, Apple have changed the way people consume both news and television.
What's interesting is that both Aniston and Witherspoon, who came to the fore under the studio system, are now flourishing in the new era.
"The reality," says Witherspoon, "is that the streaming services have empirical data that audiences want to see people of different ages and different backgrounds. It validates our audiences and it creates opportunities for new voices and new storytellers to emerge. I'm enormously grateful to these streaming services – it's changed my entire career."
And now it looks like it might do the same for Aniston, too.