<human>: My girlfriend (let's call her Diana) and I broke up early December. We were initially great, then hit a rut. The main reason is that I was an asshole who was afraid to commit.

Anyway, about a month before we broke up, I recognized a girl I once talked to on OKCupid and said hello (stupid, I know). Diana was upset, and asked me to delete her from my Facebook. I didn't, because we work in the same industry and I didn't want to alienate her as a potential future connection (Also stupid, I know). 

She messaged me while Diana was using my phone, and it sparked a huge fight.

Diana is convinced I cheated on her with this girl. I didn't, but here is the damning evidence:

* A women's chapstick in my car that I couldn't account for. Likely my mom's or sister's, but I don't actually know.

* A concealer stick (If that's what it's called. It's skin-colored makeup to cover blemishes) which I borrowed from my mom, because I get self-conscious about my skin when I break out.

* The worst of them: a pair of women's underwear in my drawer. I thought it was Diana's, but didn't think to bring it up until she noticed it (we weren't living together). It's not hers, which means it was my sister's. HOWEVER, I was still convinced they were Diana's (because I was stupid, the theme continues), so I didn't ask my sister about them.

Anyway, it's a lot of evidence that have legitimate reasons, but reasons that *sound* like bullshit.

This is going to tear us apart, because I can't convince her and she wants me to admit to it. I'm not going to make something up just to make her feel better.

Wait, should I lie and say I cheated to at least give her closure??

I love this girl. I want to get her back, but this is potentially going to stop us from even being platonic friends.

Could you distill the essence of the text into 1-3 sentences?
<bot>: My ex-girlfriend is 100% convinced I cheated on her. I didn't, and I want her back. What do?