"She was insane. She writes a book every year cataloguing their relationship, she's obsessed," laughs Felicity Jones, the star of poignant romantic drama Like Crazy.
"I'm much more reticent and cautious. It wouldn't be interesting watching someone being normal and reticent, it is mild insanity, but that's more entertaining, and maybe that's what love is."
Jones is reflecting on the unique experience of playing the part of Anna, the crazily-in-love British student who falls, hard, for Californian carpenter Jacob (Anton Yelchin) during her exchange year. Director Drake Doremus captures on film that bewitching experience of first love where all goes well until practical things like visas, families and other people threaten to prick their romantic bubble.
The film is an intimate, intense affair to experience - was it the same to film? Jones nods vigorously:
"In fact, Drake, Anton and I spent the first week just talking about our experience of relationships, because you want to understand these people, so we had to understand each other first and build them from that...
"For that month, we were immersed in their world. It felt like Anton and I had been married four times and divorced by the end of it, in some ways you go through a relationship, with the crew, quite literally, under the covers with you.
"The idea was to make it as naturalistic as possible," she goes on. "And the key to that was that we would forget the camera was there, make everything very small, and work from the inside out - you couldn't do this on stage - the camera was very close, so we had to trust Drake and be as unegotistical as possible, luckily it turned out to be okay."
It certainly did if critical acclaim is any marker. The film, despite its tiny budget, has taken the industry by storm, garnering a special jury prize at Sundance last year, and a Best Actress award for Jones, something she is delightfully ingenuous about:
"It was more of a bonus than an intention. I didn't even know there was an award ceremony. I was at home in bed and got a call to say 'you've won the acting award at Sundance'. I started screaming and running around my room."
Jones is on a roll, after roles in Gervais-Merchant's Cemetery Junction, bigger-budget comedy Chalet Girl and last year's well-received Albatross, as well as being named the new face of Italian luxury brand Dolce & Gabanna.
But the actress who made her first mark in children's TV drama The Worst Witch acknowledges that the acclaim for Like Crazy has been a career turning point.
"Since going to Sundance, I've had so many more opportunities. It's just trying to work with good directors, and obviously when you've done something that people have seen, after spending a lot of time trying to convince people of your worth, it's great to have something to show them."
This sounds like an older, wiser soul than her whimsical on-screen character Anna talking. But Jones is 27, while Anna starts out as an impetuous 19-year-old:
"I age in the film from 19 to 27. I think when you're that age, you just do things and don't think them through.
"I'm far too rational, I think about things for days and am much more indecisive."
Her eyes widen: "Get on the plane for love? No guy's worth that... but then where would the entertainment be?"
Like Crazy is in cinemas now. Watch the trailer below: