My girlfriend cheated on me.

So my girlfriend was caught a week ago texting a female she claimed to be a “friend” & while I was reading those messages they basically made plans to have sex.. the plans fell through & didn’t happen. We argued about the messages & she told me it was for entertainment purposes only.. I let it go.. here we are a week later & I go through her phone & see that she had sex with the same girl at 5:49 yesterday morning.. she was caught I 4k.. there’s pictures of them having sex & after having sex. I personally don’t know what to do… any advice ?