Found out gf has been seeing another guy for months.

I’ve been dating my girlfriend for almost 3 years. Last weekend I borrowed her laptop to print something, and a message popped up from a guy I didn’t recognize. I know I probably shouldn’t have looked, but I did. What I found was months of messages between them. They had been meeting up behind my back, and from the messages it seems like it wasn’t a one-time thing.

When I confronted her, she admitted everything. She cried, apologized, and said she made a huge mistake and wants another chance. The problem is that most of my friends are telling me to forgive her because we’ve been together for so long. My parents even said that everyone makes mistakes and that throwing away a 3-year relationship over one bad decision would be stupid.

I still care about her, but every time I think about getting back together I just picture those messages.

Has anyone been through something similar? Is it possible to rebuild trust after something like this, or am I wasting my time if I stay?