My girlfriend and myself are going through a tough time

My girlfriend cheated on me, first of all about a year into our relationship she messaged her ex partner and it was a little sus to the point where I saw the messages and she had basically asked him if he found her attractive still, she says she asked this for closure so I learned to move on and trust her again, the relationship btw has been perfect we are 3 years in and head over heels in love with each other, we don’t argue maybe get moody once in a while but apart from that it’s the fairytale couple, laugh, smiling, dates just everything you could ask for, the only problem I now face is that it’s been all ruined by one mistake, I still feel the same way to her but I have lost trust and that’s what we’re made from, she decided to download a dating app the only way I found out was from seeing screenshots of profiles on her phone, when confronted she admitted but said she didn’t add anybody or talk to nobody and deleted it within a day realising that there could be no replacement for me, she also says that she didn’t know why she did it so I gave her time to think and get back to me, her answer was that she truly didn’t know and wasn’t thinking about me or us at the time but she relates it closest to she has a very troubled past childhood family problems lots of fighting and love being broken when young she has also been through some relationships where she has been let down every time and she thinks in her later life it has taken a toll on her mental health and decision making, so in her words she said “I feel like I self sabotaged and I think that I did it because I was afraid what was so amazing was just fake like it always has been in my life and I was preparing for something to fall back on but changed my mind pretty quickly when I realised what I was doing”. I do believe in trauma and that it can really effect people at different times of there life and that sometimes there mind is cloudy and they don’t think of loved ones I completely get that but I vowed to myself if she ever broke my trust again that would be it. The hardest part I’m now going through after ending it is was that proper cheating and does she just need help like I said earlier we was the fairytale couple so is all the good we have over the years does that outweigh these mistakes because I still want my whole life with her and to grow old together and she feels the same and has said nothing but sorry and cried for forgiveness saying she would never ever do that again. What does everyone who reads this recommend should I scrap what I vowed and be the bigger person should I take this as a stepping stone just a roadblock in the relationship and grow and learn together or should I just take all the good and leave it now. Self love is a massive thing to me but the love we have built together makes this challenging.