Baby momma

So my fiance's baby momma told us that their daughter needs some plans that she only has 2. We went and got 3 more pears for now. Well today she told him that he needs to give her the receipt so she can take them back to get the money back for gas money. When we picked up the kids she was in her brother's jeans. She does have a husband. How can you say you're a good mom when you want to take back your 4 year old daughter pants back so you can have gas money and leave her with 2 pairs of pants after she bitching him out about her needing pants. Also how can you let her go out with us knowing she is not feeling good. Yes she looked okay when we picked them up but as soon as I put her in the car she said she didn't feel good then called that night saying she threw up and said she has a fever. When my son is sick my fiance will go see the kids and we will stay home so we don't pass it to the other kids and when someone is sick at my baby daddy's he doesn't get our son. There are many words I want to say to that woman but can't and it pisses me off. I have no say in the kids but her husband has all the say. My fiance and I just found out that the kids don't think that my fiance is not there. He is just someone they want to go with on the weekend and her husband is their dad. I don't want to over step about it's getting to the point where I want to tell her all about herself again and not give a fuck.