“what should i do about my cheating girlfriend”

Another soul answered...

Firstly, i'm so sorry that it happened to you. I really hope you are okay. So confrontation is definitely the starting step. I know some people might not be not that good at it but you have to do it. You don't have to be aggressive or something have a proper conversation. Ask her why she's doing it. Try to know the entire story. And to be honest doesn't matter how much duration you were with her ending things with her is not worst at this time. Because being loyal is the bare minimum you could do for someone. Put yourself first and walkout of this.

Another soul answered...

Don't lash out, first make yourself comfortable and calm, then talk to it over face to face. Tell her that you know she is cheating and tell her how you felt. Continuing your relationship after this with her is totally your choice but i wouldnt do that. Self respect is also a priority.