I have degenerative illnesses and it's something that I've always been aware of - each time there is something else that adds in or changes or that I have to find a new way of dealing with it makes me feel more and more like a burden to my husband and my children. I totally get that's how she feels.
If she's been on the same meds at the same dose for a while then it might need adjusting.
I think it's awesome that you two are talking about this and that you obviously love her so very much!