Is this selfish or unreasonable to demand?

Your wife isn't punishing her daughter properly. She lets her get away with it and doesn't keep to her punishments, that will be why the kid will always do this because she knows her mother doesn't really do anything about it. Maybe the mother feels guilty she's not with the kids father anymore and feels sorry for the kid, therefore to compensate she sticks up for her when she does something wrong, instead of punishing her. But if the mother has the nerve to tell you, your coming between her and her daughter then it sounds like she's using you. If that's your place the lease is in then make the mother pay for her kids damages, why should you pay? Maybe if she really feels your coming between her and her daughter then you 2 should separate before the kid makes it even worse for you, (like jail) for some story she might make up to get you in trouble, you really don't need this in your life. But the mother should realize that the kid is under your roof also and it is your right to punish and set rules to. Who needs a wife that will be outraged because your coming between her and her daughter doesn't sound like they need anyone else in their life, just someone to foot the bills. But when the kid grows up and leaves home, that's when it will sink into the mother when she's sitting at home alone with no-one because of the kid, that she should have sided with you on punishment and rules, instead of saying that to you. You might want to seriously think about getting out of the marriage before it becomes worse.