The pop star, 28 – whose split from ex-husband Russell Brand was briefly exposed at the end of the movie – struck a chord with fans – among them, Lauren Conrad.
"I saw it on a plane and started tearing up," the former Hills star, 26, told Lucky magazine in its March issue, calling herself "really cheesy" for getting misty-eyed over the documentary.
"The movie touched on her divorce and how she had to go up on stage every night. She's crying as she goes up, and once the lights go on, she just smiles and pulls it off, and you're like, 'Wow.' "
When it comes to Conrad's own love life, she seems in a comfortable place with boyfriend William Tell, despite their different schedules.
"He studies all weekend," she explains of the USC law student. "I've been working. I'm renovating a condo, so I've been spending my weekends shopping for home stuff at flea markets."
The fashion lover adds that her beau doesn't share the same tastes – not that she minds.
"He just a jeans and a T-shirt guy, which I like," Conrad says. "I like no-fuss style. Sometimes I'll buy him clothes and sneak them into his drawer."
As far as her own style is concerned, the TV personality admits she wasn't always the fashionista she is now.
"I try to never look back at how I dressed in the first few seasons of Laguna Beach because it was pretty bad … head-to-toe bad," Conrad says. "This past summer, MTV replayed every episode and I would always see it and be like, 'Ahh, no!' I wore these capri denim pants a lot and they were so bad."