Bearing in mind that I know nothing about these people and their financial state, etc:
Could mom buy herself and girl tickets to somewhere fun, but far, with BAD cell phone reception (or accidentally spill her drink on girl's phone) and surprise girl with this "fun trip?" My first thought was out of the country, but that would be close to impossible to pull off without girl's cooperation. But going to, say, Alaska? Or Puerto Rico? Or, really stretching here, Guam? ;) Seriously, to me it would be worth a lot, and a lot of debt too, to keep MY dd out of an icky relationship like this one. I'd move heaven and earth to keep my relationship with her and keep her out of his clutches.