Temporary custody help?

I am trying to find out answers for my fiance's sister- in- law.. She gave temporary custody to her mom years back. This was done in fl. She just recently moved to nc. Her mom is now calling her saying that she is going to get a notarized paper giving the son's ex step dad rights to take care of him and giving the son to him who is not the son's father. Can she do this? Does she have the right to do anything custody wise besides giving the son back to his mother?