Unusual situation regarding promotions

Unusual case, I typically have an answer, but this is odd. My Fiancée works at a major fast food chain store here in New Mexico. Since being hired, they have tried to get her to become assistant manager. She has declined on several occasions, but eventually has taken a promotion to shift-manager. Her reason for not taking promotions has been explained, she goes to college, and does not want too much responsibility that will interfere with her studies.

Here is where I get lost....

They have just asked her if she wants to move to another store and become primary manager. She declined the offer, but was told today that she is being moved over there as manager whether she wants it or not. They have even given her a schedule to work out for the other store without sending her to the appropriate training classes or knowing anything about this store. She is terrified at taking this position, and is not prepared to take on the additional responsibility this presents. She feels that after working for nearly three years there that she should not be forced into this.

My question is what recourse does she have? This particular chain has been known to promote people and then fire them if they can't perform the way they want as opposed to demoting them to the positions they worked well at. Any help would be appreciated.

Is she an at will employee?

As far as she knows she is not. We live in New Mexico, and she works at a national chain restraunt. I will have to look into it. Thank you for such a quick response.