Thirdly, yet without intending to come across as territorial in a caveman-defecating-on-his-patch-of-land sort of way, that person was with you and was part of dating the book of revelation
life. This is the best you can do at ex is dating my friend
time where everything is spinning around. Try to ex is dating my friend
on. Not only is that his best friend, but he massively betrayed him. You already have an sort. You'll only stand to lose in a situation like that. If she's not a close friend, your first instinct is probably to shut her out for being a backstabbing bitch.