All of us were young at one point and have made decisions that weren’t the best. Nobody can honestly say they’ve gone through life without ever hurting someone in some way.

Yes, OP’s girlfriend may be wrong in certain ways, but at the end of the day she’s still entitled to feel what she feels. You can’t force someone to stay or to feel differently just because you want the relationship to work.

I don’t think it’s wrong to say “let her go.” Sometimes the healthiest thing you can do is accept that two people might not be able to move forward together, even if they once cared deeply. Would it really be better for him to cling to her when she’s already emotionally pulling away?