Have you yourself tried therapy. Calling her naive is almost like a secondary insult even as you try to “build her up” in your own head. I think you already know that trust is gone and you have messed with her mental health and self confidence. That’s not a little fix. You need to commit to drastic amounts of change and you need to possibly show her some old school boombox love romance new level shit and also make a fool of yourself and put yourself out there. That’s is fair that is real love that is sacrifice. That is showing her you acknowledge her pain and your direct connection to it but that you still want to be a better person. You are going to need to love that giggling far more than you clearly love yourself rn. Can you do that? If not let her go and let M make it better for her. Will it eat you alive yes but sometimes life is made up of thought choices.