Promised a promotion, but someone else got it

i just found out that my job is making someone else a manager even though they've been promising me a management position for almost a year now. I'm more experienced and been there longer than the other employee. Im angry and hurt and I dont really kbow what to do. I want to talk to the gm and ask her about it but im really anxious about confrontation. I'm also considering putting in my 2 weeks. I have been calling off more than usual lately, but its been for legitimate health reasons, not cause i dont want to go in.