I think that's a great idea. We can hope that your sister will have an awakening...but in the meantime a couple of simple things might do her good. I like the idea of the bath. There are a few different kinds posted on the Bath Forum.
Now...I think that AFTER the bath she should massage olive oil into her body....feet, legs, stomach, as much of her back that she can get to. It may sound strange, but Edgar Cayce suggests this for skeletal problems. (he actually suggests mixing olive oil and tincture of myrrh together - but if myrrh is too complicated I'm sure that olive oil will do - many of his remedies recommend an oil of sorts being massaged gently into the joints etc to be absorbed by the body...)
This could be a nice routine for her...baths and then massaging in the oil...