Her estranged husband, comic Russell Brand, blew his top when TV host Graham Norton brought up the impending divorce.
But despite Katy’s PR people hovering near us in her Los Angeles hotel suite, the pop princess nods sadly when I say she must have been through hell.
Katy, 27, clearly isn’t your typical image-controlled superstar, and she opens up when I ask her what she has learnt from the past year when she had to cope with that very public marriage split.
“I’ve learnt I’m in a very modern fairytale,” she replies after a moment’s thought. “But I also know I don’t need the Prince Charming to have a happy ending. I can make the happy ending myself.”
Then, knowing I’m from London like her ex, she adds with a wink: “But I still like London boys… except one.”
Katy’s honesty also shines through in her new 3D documentary, Katy Perry: Part of Me. Made by British film-maker Dan Cutforth and New Yorker Jane Lipsitz, it follows Katy over the course of a year when she had phenomenal success with hits such as Last Friday Night (TGIF).
Her album, Teenage Dream, became only the second, after Michael Jackson’s Bad, to produce five US No1 singles and her California Dreams tour featured 124 arena shows across the US, Europe, South America and the Far East.
But the 300 hours of footage shot over the year also show her curled-up, crying and barely able to move as the emotional pain hit home when Russell filed for divorce.
In one heart-rending scene, Katy is in pieces backstage at a gig in Sao Paulo – but somehow slaps a smile on her face and performs.
“I could feel the energy and support from my fans,” she said.
“Just before I started a song, they kept saying in Portuguese, ‘Katy, we love you’ and I felt comforted by that.
“Watching it in the edit suite later I was saying, ‘This is OK’.
“I’d just needed a shoulder to help me walk up the steps. I had to bend over so my false eyelashes didn’t come off.
“I couldn’t let the tears stream because it would ruin the make-up.
“But I got through it. I’ve learnt a lot and am moving forward one step at a time.
“It was a year I’ll never be able to recreate. It had amazing highs and some big lows, but that’s life.
“Everyone goes through the good and the bad and it makes you stronger. But my ultimate goal is to make people smile.”
It’s difficult not to smile when talking with Katy. She has an infectiously bubbly personality and laughs a lot. But she is also wise beyond her years.
The singer, famed for outrageous costumes, is wearing a white sequinned dress and her long, dark hair is tinged with purple.
She has a tattoo on her inner wrist that says in Sanskrit “Go with the flow”.
Katy learnt to play guitar and sang wherever and whenever she could.
She said: “When I was 13 I’d sing on the corner at open air markets and put my guitar case out.
“People weren’t sitting listening, they were just passing so there wasn’t a lot to be nervous about and I’d make maybe 10 dollars. It was a nice way to start.”
She released a Christian pop album under her real name of Katy Hudson but it only sold around 100 copies.
Then she landed a contract with Capitol Records, shedding her Christian roots and good-girl image and zooming to the top of the charts in 2008 with the album One of the Boys, which featured the cheeky single I Kissed a Girl.
She dated several musicians, including Travie McCoy, of Gym Class Heroes, before meeting Brand while filming a cameo for comedy film Get Him to the Greek, which the comedian, 37, was starring in.
They were reunited at the MTV Video Music Awards and announced their engagement in January 2010 after a four-month courtship. They married in the October but he filed for divorce 14 months later, citing irreconcilable differences.
The marriage had started to crumble while she was on her year-long tour.
Katy says she tried her hardest to keep the relationship going, adding: “Being in love is the dream.
“But the reality of making it work is not like the movies.”
She also recently said: “I really wish I had more time to be cuddled right now, but I don’t. And I am very particular.”
Katy tells me that watching the two-hour film was strange and uncomfortable.
She said: “There were things that made my tummy turn when I saw them because I had already lived them and really didn’t want to live them again. But I thought maybe if I showed I got through the problems, other people wouldn’t feel so alone in their problems.
“It was important to leave some of the more difficult things in the film so it wasn’t a narcissistic film about how great I am. Because I’m not all great.
“We all feel our problems are unique but we all go through a lot of the same things and it’s not about the problem, it’s about how you solve it.
“So the whole movie is about me overcoming obstacles, my upbringing, the guys in suits from the record labels and then my personal struggle – going through it and landing on my feet.
“The message is pretty simple — it’s ‘be yourself and you can be anything’.”
If you’re Katy, being yourself is a combination of fun and hard work.
“I like to have fun and get crazy but I do that in my private time,” she said.
She is also working on starting a record label, writing songs, planning an album and promoting the film.
“What holds me up is focus, determination and an incredible ambition that hasn’t subsided yet,” she added.
“I know I have been given something great and I have a certain responsibility so I try to keep a moral compass about me in everything that I do.
I ask the karma gods if this is going to turn me into something hideous, or if it’s going to be good for me.
“It’s been a long journey of learning, tolerance and acceptance because I’ve met different people and travelled a lot and educated myself instead of wandering around aimless and ignorant. I hope to evolve every day and be a better version of who I was yesterday.”
Despite the heartache, Katy says that she is still a romantic and hopes to have a family.
“I want to be a mother but now’s not the right time,” she revealed.
“A baby can’t have a baby, and I’m still a baby.”
When I ask if she is afraid of falling in love again, she says: “No, absolutely not. I’m excited for the future, whatever it brings. I still believe in love, most definitely.”
By John Hiscock
