<human>: So my gf and I broke up about 2 months ago. Things just weren't working out, but we both really liked each other. I sort of moved on, but a couple of weeks later she kissed my best friend. Then, about a month later she came to me and told me she wanted to get back together because she really liked me and missed me. The thing is, I said yes, and we've been dating for a few weeks now. I found out yesterday that she kissed my best friend from a third party. I confronted her about it, and she said she was going to tell me but she didn't know how, and she didn't want me to end things.

What should I do now that I know she kissed my best friend and she didn't tell me, even though we weren't together at the time?

Summarize the given text in a few sentences.
<bot>: My girlfriend and I broke up, she kissed my best friend, we got back together, I found out yesterday that she kissed my best friend when we broke up. Advice?