Getting called mommy

Cheyene
So I babysit my neighbors son while she works nights. He's just turned 2 and is only now starting to talk (mom keeps a Binkie in his mouth all the time). I have him all day (he goes to my daycare) even on her days off, i bring him home when i leave work, then when she works I have him till 11 at night. Well lately he's been calling my boyfriend Da-da and the other day when he went outside to get something out of the truck Junior go in the window and kept saying Daddy, and from time to time I'll hear him call mama but I just thought he was calling for his actual mother till today when he came yup to me and called me Mommy. His mother is almost 30, with 4 Kids but only has custody of him. I feel bad about his situation right now because she's more preoccupied with keeping her boyfriend (who hates kids but she and Jr live with him) happy then taking care of her son. On the days she works I have him from 10 in the morning when I get to work to almost 11 at night when she gets off, and then all she wants to do is go over to our other neighbors house and drink, on his second birthday last month she was so shit-faced she couldn't even put her own son to bed on his birthday. Idk what to do...