I'll be honest and say I have very little experience with them. That said, what is it that attracts her to them? The online classes? You'll find that most of the large universities offer many degrees that can be taken almost entirely online and would be a fraction of the price.
Also, while I would consider them more seriously for an undergraduate degree, I think that using them for something as considerable as a Master's would be out for me personally. That's just my opinion though. Employers (and if she wants to go even further, graduate schools), will take where you got your graduate degrees more strongly into consideration than where you got your undergrad.
One last thing to consider: Is there another university (maybe state or something) that accepts transfer credits from UPhoenix? If so she could perhaps take some classes through them and see how it's going for her, then transfer them into another graduate program, where she would actually get her degree.
May I ask what she wishes to get her degree in?
Nexa
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“It has always been the prerogative of children and half-wits to point out that the emperor has no clothes. But a half-wit remains a half-wit, and the emperor remains an emperor.â€
― Neil Gaiman, The Sandman, Vol. 9: The Kindly Ones