Try giving her Tylenol before her evening bath and then let her sit in really warm water while it takes effect. The warm water on her legs will cause her circulation to increase there and that will bring the Tylenol directly to her legs where the pain is. You might want to try children's motrin. It is made specifically for muscle and joint pain and lasts longer.
Also, make sure that she eats plenty of bananas. They have lots of potassium in them and insufficient levels of this mineral cause leg cramps. When my dh was working building railroad tankers in Texas, he had to take potassium supplements every day to replenish what he would lose when he was working and sweating. If he didn't, he would wake up in the middle of the night screaming in pain (this is a 6'1", 200+ lb man) because of the leg cramps.