Should I take back my cheating ex? Tricky situation, please help :)?

So last week my then girlfriend dumped me. It was all very unexpected because I didn't see it coming at all, we were so happy together. She gave some stupid reason which I didn't buy for the break-up. Turns out, just like I suspected, she made out with another guy. I found this out from my gf's best friend's boyfriend. Here's the story:
She went to a small party with her coworkers. They ended up doing mdma (she took 3 hits and she's a novice), drinking (15 drinks), and smoking weed. She was very fucked up. There was a guy at the party that I knew she was very sexually attracted to (supposedly she didn't know he was going to be there). Anyway, him and my girlfriend spent a lot of time together and it sounds like he was taking advantage of her state. My girlfriend was grinding her teeth like crazy and he said they should go get gum. They went to get gum (it was only a 5min walk) and he ended up walking her to a park where they talked. He asked her to hold his arm and then he kissed her. They had a full make-out session for about an hour, then went to the party.
Anyway, girlfriend tried to hide it from me but something seemed off and she told me that he was hitting on her but said she never cheated. I trusted her and put it behinds us. The very next day, she dumped me. I know it'scrazy that I want her back and that I shouldn't, but she was extremely messed up and I can see how it can happen without her even thinking it's a bad idea at the moment since I know I've done things on mdma (just 1 hit, let alone 3 + everything else) that I normally wouldn't have. She also did break up with me because she felt so guilty and she felt she didn't deserve after that. My source also tells me that she's not taking it well and knows how badly she fucked up and that she can't believe she did what she did. I am deeply in love with this girl. She's going to be moving to another country in 3 months. Should I take her back so we at least have 3 more months together?
Should I take back my cheating ex? Tricky situation, please help :)?
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