Man. I used to work for a place like that, and after leaving, I found out that re-scheduling like that is typically against most 'rules' in place by labor boards. Typically you need at least a weeks notice for your shifts, unless you have agreed to be on call and agree to the changes made. In my area, it's 2 weeks, typically.

Depending on the company (I won't ask), you should consider calling in to someone higher than the person scheduling and lodge a complaint. Don't settle for the: "Things change and people have to adapt because they need to" BS. I used to be given that run-around. When I started my new job (government) and spoke with the HR lady about previous problems at my last job, I was informed than many of their practices go against policies and labor codes in place to protect employees from unreasonable expectations.

Definitely raise a fuss, if you are able. That type of re-scheduling is unacceptable. A tweak here or there, yes, I can understand. Full re-scheduling.. That's not your girl's fault and she shouldn't have to put up with someone else's inconsistencies.