Sit her down and tell her that if you aren't respected in your shared home as at least an authority figure (like any adult would be)then this isn't going to work.

Mom should be the one the kid had to listen to. Sure, you have the right to have house rules and expectations, but mom needs to be the nagger and enforcer. If you try to fill this role, you are merely allowing yourself to be pigeon holed into the bad guy/scape goat role. If she's a crappy parent and that's a deal breaker for you, then let it be the deal beaker.

Tell her. When I married my husband I was happy to have someone else help me with disciplining my kids. Maybe she doesnt even realize what she's doing. She might be so used to doing everything herself. You really have to set a standard BEFORE you get married.

Funny you should say that she must like it for some reason. I often get the impression my DH likes the fact his son is disrespectful to me, I can't put my finger on why that is though. Like he enjoys seeing his son act like an ass. Funny, somehow I don't see how an 8 year old lipping off or blatantly ignoring an adult in the home is teaching him anything good.... but that is my opinion... which I keep to myself.

I no longer ask\tell\expect anything from SD14 or SS8 - i disengaged. However, that doesn't mean the little crap doesn't totally get to me. Like DH drives SD to school every morning, during that time SS is here with me, DH tells SS to finish his homework and stay off the PC like clockwork, the garage door closes and SS is in the PC playing games, the garage door opens, he grabs his homework and sits down pretending he wasn't playing games. He does this right in front of me.

Why don't I say anything you ask, well, before I disengaged, I used to shut down the PC which SS would melt down and DH would return and Iw as the the evil SM, then I resorted to just informing DH when he returned to which DH would 'scold' SS and I was the bad guy for telling on him, DH angry with me because it forced him to parent, to which I disengaged, the most I do now is once and awhile when I can't keep my mouth shut I will make a comment like, man, you must be done your homework, to which SS either ignores me or just lies to my face which just makes me more angry.

So 99.9% of the time, I just say nothing. How pathetic is that.