What would you do????

That is not cool. No one should have to change like that in a relationship. She shouldn't have chose him over you. You sound like a better person and she was really close to you. Unfortunatly people go through this and eventually realize what they have done was not a good decision. Anyways just try talking to her and offering help if she needs it. Tell her she is being treated very badly and can find someone else who will treat her better. Hope this helped and good luck!