i (27m) in a healthy relationship with my gf (25f) found texts from a drunk ex fwb in my gfs phone

my girlfriend (25f) and i have been dating since a year.

we’ve had our fair shares of hookups in our past but now i’m very certain of never bringing my past into our present.

however yesterday night i saw her replying messages from her ex fwb (we share ig passwords) who was claiming that he is drunk & has a habit of texting her whenever he is so. i hate the fact that she was leading him on. at no point of the conversation she tried to shut him off. it was borderline flirty imo. messages like, “and? what is it about me that brings you back to me?” & the guy went “you’re impossible to forget.”

we were on call when i saw it, (she was texting him despite being on call w me) i lashed out & immediately blocked her. did i overreact? she’s been texting me everywhere since morning saying it was a “bad lapse judgement” she felt bad to leave him drunk and alone. but that makes no sense to me. did i overreact?