Sorry, it is not always as simple as that. With kids maybe yes, with teens and young adults bullies are sometimes just evil. I've experienced bullying all the middle school and most of the high school. Not showing weaknesses to them and faking power didn't help at all, just made things worse.
OP, speak to your friend. Don't expect them to break up, but just explain that you will feel better if you both could spend some time without that guy around you. See how she reacts.