Do you this that this is right?

Ok here is a long story short. My fiance and his ex have a son together, he is 5 soon to be 6 and very smart. Honestly I dont think that she cares about the kid, just the money. She basically uses him as a pawn because she knows that his father cares about him so much. Now here is the probelm: She takes her son to her mothers for daycare. Now I dont see this a a problem becuase she is a licesned daycare provider. The thing that bothers me is that she gives us copies of the recipts cause he is supposed to pay 1/2 of the daycare, which is fine. The problem is that all the reciepts are is numerical order, one right after another. Does she not give out any other reciepts? When the were dating she never paid her mother for daycare, and to this day i dont think she has. She took him to court cause he wasn't paying, and he has to pay daycare as far back as 2005. We started dating in Jan. 2006. Does this seem right to anyone? I just dont think its right. And what should we do?