I had been paying money each month to Mom's nursing home, but the billing lady said that I had a two month credit on my account because Medicaid had been paying the bill. Has anyone ran into the same situation?

My mom when into a nursing home late Dec. of 2016. I filled out all of the paperwork. The first question is are you suppose to get copies of everything you sign? The next question is, I signed a paper that said I would have to write a check of all of her Social Security except for $50.00 each month. I stared doing that, but when February came, the lady that does the billing said that I had a two month credit on my account and to quit paying as Medicaid has been paying the bill. She sends me a statement every month showing a 2 month credit still. She told me to spend the money on things Mom needs as I cannot have that much in her account. I'm afraid that they will come back and make me pay it back or kick her out. I'm just not sure which way to go on this. Has anyone ran into the same situation and how did it end.
Feeling concerned and confused.