Best friends boyfriend cheating on her!!

Vivi

So first of all my best friend is not my best friend anymore I haven’t talked her in over a year because of her boyfriend she cut off all of her friends ☹️

I am just asking for advice on whether or not to tell her that her boyfriend is cheating on her! I always see him out and about and he is also hanging out with a younger girl. Some people tell me yes tell her and some people say no because she left me for him

What do you guys think?