ADVICEEEE !!!!

So 2 months ago before me and my girlfriend started dating she kissed another girl then came to kiss me RIGHT AFTER! And I was so upset! How could someone do that to me? But I forgave her and decided to give her a second chance, Bc we weren’t in a relationship yet, though it’s the principle.

So 2 days ago she addressed me

Her: I think we should take a break

Me: why ? What’s wrong ?

Her: nothing I just need some space

Her: does this mean we can do things with other people?

Me: why, is that what you want... to do things with someone else?

Her: no.

Long story short that IS the reason why she wanted to take a break because “the opportunity has presented itself and she has been waiting for it” so I broke up with her and cried in her arms and she begged for me back. And she still wants to have sex with this person. But hasn’t did it.

Should I stay broken up with this person orrrrr? Bc technically they didn’t cheat. But it’s the principle why leave someone you “love” for some other pussy?