Step parenthood

How do you deal with it? Your stepdaughter is saying how her mother's husband(which is her stepfather) is always treating her different, when she and the rest of the kids go out to eat she has to get the cheapest item on the menu,when the others get to get whatever they want no matter the cost. She is always telling me how he talks to her very badly when her mother is not around, see me and my husband( her real father) get her on the weekend, so during the week she is saying how her week went and what was done, I never have to discipline her because she listens very well but her stepfather is always pointing out that she is not his real daughter so she doesn't get the Same privileges like the other kids and he don't have to do for her whereas her mother has to do for everyone she doesn't look at the fact that the other kids are not hers.

I've been wanting to say something for the longest but didn't know how to bring it up because she asked me not to say anything but this is going way to far

What should I do I need help to solve this problem very peaceful