Perhaps when she is doing roll ins, she is pulling or straining the hamstring tendons. Two groups of connective tissues at the back of the knee and thigh, that connect some of the muscles of the knees. Just a possibility.
Hard to make an educated guess, without watching her form, and seeing what part of the knee is causing pain.
I would suggest watching her form. Seek professional help if the pain continues, or becomes worse.
Sorry, I can't be more helpful. Good luck, hope it starts improving on it's own.