We were in a 10 month ldr. She cheated at the 7 month mark and hid it from me. I came back home and surprised her, and her reaction was something I'll never forget. She looked scared to see me. Yet she approached me and kissed me on the cheek. She later kisses me on the lips in an odd way while going down some stairs (she basically stole the kiss when I wasn't paying attention), and then proceeds to tell me "I have to tell you something, I cheated on you". She later explains the kiss as "I owed it to myself after not seeing you for a year" or some bullshit. What does that even mean?

I went radio silence for days while she kept texting about how she can't lose me (as a friend I guess) and I relapsed once and texted back and regret it.

I'm not taking the breakup well. I haven't been able to eat or sleep properly for days. I feel like worthless shit and I am ashamed of it. We're in the same group of friends so I have seen her once after the fact, and I am seeing her tomorrow. Should I not attend these gatherings? Wouldn't this mean she's won? Should I accept what happened and be cool around her, say hi and bye, and make very small conversation? Should I text back dry replies when she texts me to avoid looking butthurt or completely ignore? Should I talk to her about my feelings and what happened for closure (my heart tells me I want to do this, but my mind tells me I shouldn't)?

I have a month left of my vacation. I had such high hopes for coming back and seeing her again, and enjoying my time with her here. We're both going back to the same state next month. We had plans to see each other often, and continue the relationship back in the US. I fucking hate life right now, I am going out with my friends and I am not enjoying my time. I can't get images of her cheating out of my head. She used to write me love letters about how we were going to be together again after the ldr, how it would take effort but we could do it. She later claimed those were "very cheesy letters". How can someone claim to be in love one second and not give a shit the next? It fucking hurts.

There is one question lingering in my head right now. It keeps repeating over and over. "Why?" I want to say it to her. I don't know if I should.