I am assuming direct control.
Coincidentally, I went through almost the exact same thing. My best friend got dumped on his ass, and I tried my best to cheer him up. It was fine for months before his Ex wanted him back. He was so blind and gullible that he let her play him like a flute for weeks. She convinced him to dump his GF at the time and get back with her even though at that point she had been involved with three dudes. She tormented him emotionally, using his friends, family, and even her own parents against him. She would insult him on a daily basis and then text him saying he would never be happy without her. It was the most disgusting act of exploitation, but of course he felt sorry for her and gave in.
Needless to say, I was livid. His girlfriend that he dumped for his Ex went on to suffer depression for months because of how he treated her. His Ex split my group of friends by nosing her way into everyone else's relationship. Fast forward to present day, and what was once a close knit group of bros has become a mockery of its former image. My closest friends turned on me with her influence and those who stood by me hate her for her actions. It was supposed to be senior year full of fun and games, not putting up with whore girlfriends.