J.S.
I am kind of confused as to what you are asking. FMLA is 90 days per 12 month period. It is unpaid and only firms with, I believe more than 50 employees, are subject to it.
So she can take 12 weeks, unpaid, end of discussion. If she takes 12 weeks, one day, they can legally fire her. That is all FMLA is, it is a law to protect employees from being replaced because they needed to take off to take care of their family.
Oh and FMLA is federal, it does not vary state to state. Some states offer other things that run parallel to FMLA but it isn't FMLA.