Thanks for reading, english ain't my first langage.

So, i was invited to my friends birthday supper. I cheated on my LTR when she was out of the country for visa reasons with a girl of this group of people.

My girlfriend didn't want me to go to the supper because she thought that this girl would be there and she wanted me to take her side and not my birthday buddy. I told her she could come but she didn't because she has her honor to save and those people would talk behind her back. (they probably would but a lot of them won't give a fuck)

It was either i'm going and everything ends or a stay with her. She also don't want me to see those ppl cause it reminds her that i cheated.

I didn't like that ultimatum and i flinched (broke frame basically) Now i'm thinking she's gonna use this against me anythime she want's.

What should've I done? What should I do next? How can I not be in this situation again? Other commments?