Fed up!!

So it seems like all my problems r with my step kids’ mother...I’m really a laid back person n don’t usually let anything get to me, but this has been an ongoing issue...husband had court on the 2nd of this month but they had an issue with court calendar so they pushed it to the 17th...so we r trying to modify child support because youngest one lives with us n been living with us for like 6 months to a year now...oldest hasn’t been here at all even when they have an order for about a year now...she is 15 now...her mom allows her to drink, smoke n have boys over...my main issue is that the mother n other kids go on trips n leave the youngest daughter out because she lives with us...she had just recently taken her son(that my husband has raised since he was a baby but isn’t biologically his) n a friend n her son to Lego land n didn’t even take her...his son came over this past weekend n was telling her about the trip n she asked y couldn’t she have gone...now this kid is 6 years old n his response was that she doesn’t live with them anymore...now to me it seems like she is punishing her for choosing to live with us...n she still receives child support from my husband...really sucks that I can’t do anything about it..she has even asked to go on trips that they r planning on in front of her n she has told her no..really really is frustrating...I have kids with another man but he hasn’t seen them in a long long time..but when he was at the beginning of our break up, I never told him no to taking his kids or never treat any of my kids differently...I also adopted three of my nephews n I do not treat anyone differently or favor one more than the other...if I buy one toy for one kid I have to buy something for all of them...how could a mother have sooo much hate to treat her child like this??? Or am I just over exaggerating???