You shouldn't get in between your friend and their partner.
Jimmy best friend's girlfriend tells him she's not sure about the relationship anymore.
Jimmy wants to respond to his friend's girlfriend.
Jimmy tells her she should be talking to her boyfriend about it, instead of him.
Jimmy tells her he'd be a better boyfriend, and she should leave his friend.
Jimmy's friend's girlfriend appreciates the advice and has an honest discussion with her boyfriend.
Jimmy's friend feels betrayed and stops being friends with Jimmy.