Ex wants us to leave our current SO’s and get back together. Hell no

I’m insanely in love with my boyfriend and would not leave him. But my ex is “still in love with me” and said he’ll leave his girlfriend for me if I leave my boyfriend. I obviously said no. But should I tell his girlfriend? I’ve been through so much drama back and forth with this boy for TWO YEARS. I just want him out of my life now so i can be happy with my current boyfriend. She deserves to know, but in the past every time I’ve told a girl something like this she ends up bitching at me and staying with the boy. All I’ve ever made by telling girls is enemies. So idek. What do you guys think