Best friend

Nxkki

Hey y'all. So i have a best friend and she is in a long distance relationship with her boyfriend.

Her guy has always been with girls all his life. Now that they've been dating and he really does loves her ... Him talking to the girls makes my friend really insecure and she's been panicking and getting anxiety attacks. I really want to help her out and her boyfriend is asking me to help her as well.. how do I reassure her?