I'd take your mother-in-law off the Lipitor immediately. Her intuition tells her that the drug
is making her nervous. That's probably just one of
many bad effects it's having. Prescription drugs
are deadly.
Her cholesterol levels are a MUCH smaller problem
than the errant behavior which is probably caused by
the drug. In your place, I would take her OFF the
Lipitor ASAP. At the very least, try it for month,
and see how she responds.