Anna Kendrick says she spoke to the woman her ex cheated on her with

Anna Kendrick has opened up about discovering her ex was cheating, confronting him and reaching out to the other woman.

The Pitch Perfect star had her suspicions that her long-term partner - who she did not name - was being unfaithful, and her suspicions were confirmed when she unearthed messages sent between the two.

"I ended up finding out some capital T truth and was exposed to year-long text exchange and went, 'Oh, I was right about everything. Oh, OK,'" the 37-year-old recalled on Dax Shepard's Armchair Expert podcast.

"It was actually way worse than I even thought."

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Her partner had previously vehemently denied any wrongdoing during couple's counselling.

She said: "He is screaming at me, 'It was a passing crush, you're so insecure, I never saw a relationship with this girl, I even told my best friend I never saw a relationship with this girl.'"

These messages weren't ambiguous, either.

According to the Twilight actor, one such text read: "After a week of f**king you, I want to blow up my life for you. Just say the word and we'll ride off into the sunset together."

In the face of this evidence, her ex still denied having an affair.

"To know, oh no, you said it and I didn't actually think that you could lie to my face with such intensity and conviction," she continued.

"When I confronted him on it, he said, 'I don't know what you're talking about.'

"Which, again, was kind of a relief, because you go - 'Oh, you're pathological. This is in black and white.'"

At this point, many people would have booted out their partner and left it at that, but Kendrick decided to reach out to the woman he'd had an affair with.

She explained: "I ended up emailing this young woman and saying, 'I just think it's fair that you know that I know. I don't put this at your doorstep. You made a mistake, but you're 25. We've all done stupid s**t. I very much lay this at his doorstep. I just wanted you to know that. I don't know why we would ever be in a room together, but if we were I just kind of need you to know. If I were you I wouldn't want to talk to me, but if you ever wanted to talk I'm more than willing.'"

Surprisingly though, the woman did get back to her, and it seems the conversation helped them both.

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Kendrick said: "To her eternal credit, she was like, 'Yes, can I call you?'

"We talked on the phone for about an hour and she was just like, 'I'm so embarrassed and I'm so sorry... This was a mistake.'

"To just for like an hour be honest, that's all she did was just say, 'I'm so sorry, I feel terrible, and yes, this happened.'

"I hadn't eaten in a week. I couldn't sleep. I couldn't eat.

"I had this conversation with this girl and we hung up and I was like, 'Oh, I need a plate of nachos.'

"My whole body just went, 'You can grieve. You're not crazy. You're safe. You can grieve. You can eat nachos. You can have a glass of wine.'

"It was like my whole body got whatever it needed. It at least stopped that total panicked state that I'd kind of been in for a year."