I get toe and now leg cramps quite often. They can be caused by dehydration, low potassium, low magnesium, and muscle loss (most likely why I have them), and others problems as well.
I don't know how old your mom is, but it could be muscle loss in which case doing push ups against a wall stretches the muscles. That's working for me. Older people tend to not drink enough because of having to get up to go to the bathroom. Too many things could be causing the cramps so have to agree that she see her dr. for testing.
sdm52
Kidney?? The pain would be on one or both sides of her lower back not her leg. Speculating the source of her discomfort can be endless without a thorough examination. Best to see her PCP for an evaluation and go from there.