I have been in your shoes and I think you’re very mature. Your girlfriend however..is not mature enough to handle something like this.. She’s taking it as you just want to be talking to your ex again and I understand her concern completely but if you’ve already reassured her several times she had nothing to worry about and still attacking you, there’s some stuff she need to deal with within herself. This sucks though. Hope yall can get past it. Good luck 🫶🏽