Do I have a right to be upset?

Ok so I need some advice.. I am in love with a man who has two beautiful daughters, and I also get to put up with his ex.. I have a hard time when she calls because she bragged to me about how bad she treated my boyfriend when they were together.. I mean, who does that!!!! She told me so many horrible things it is extremely hard when I hear her name her voice or even hear the girls talking poz about their mom. I love them and I want to do what's best.. Do I have a right to be upset? She even tells us we have to pay her money if we want to see them.. Wt!!!! We take such good care of them. We get them for the summer and holidays. Even though she wants them again early.. Does anyone know or have advice for me.. I have never known such a money hungry and selfish woman. I am crying while I write this.. It just breaks me.. My heart hurts for him and for the girls... What do I do... Please help... Ty love, Ramona