Things my now ex girlfriend did but didn’t tell me

So me and my girlfriend of 5 months where together we are both freshman’s in high school and my best friend who I knew since elementary he was like dude I need to tell you something and basically he said was she like sent nudes to her ex and like blew him and had sex with him and like when he tried to end things she basically manipulated him into staying but don’t feel bad for the guy he was also horrible like stalking her following her home and stuff but when he told me that I was shocked because she said she would keep no secrets between us and I just felt like empty when he told me that because I loved her like she is beautiful and like I felt betrayed when he told me but she doesn’t know that he told me and her mom forced us to break up because her parents are strict and I just like feel weird because this was my first girlfriend like ever so I just don’t know if anybody can help me forget about it that would be amazing.