I'm no physiologist, I'm not a doctor, and I'm not even close to being as smart as a lot of other folks on this forum when it comes to this stuff. I'm only giving input on what helped me out (and a bunch of other jacked up military folks in my yoga class lol) with the possibility that it might help her out also if it she wants to give it a go.
And I'm not some neo-hippie that believes that yoga cures cancer and helps you achieve universal-infinite-supernatural-oneness. I couldn't even come close to telling you what about the class helped my knees out. Could have been stretching, sissy strengthening of my leg muscles, voodoo, I have no idea. But something during the time spent doing it helped them out, the gal sounds like she has very few options on what she can do, so maybe this might work for her.
If I'm wrong, that's cool. Call me on it. If it sounded like I was offering yoga as a cure for all ills and sins, that was not my intent.