sounds like she should see Angiologist do ultrasound to her leg?
She definitely needs to go see a doctor. Does she have diabetes? She could be having a circulatory problem in her feet that could be serious. Just because it doesn't hurt doesn't mean it's harmless.
Muscle cramps are more common as we get older. Leg cramps can come from low levels of calcium, magnesium, potassium, or vitamin D. However, there are lots of other possibilities that are more serious, such as circulatory, liver, kidney or thyroid problems. A doctor can help determine what is going on.