WOW WOW WOW I am here to tell you I know your story well...I am a therapeutic foster parent in belmont county and let me tell you I have lived this story about 12 times.
1st of all...she has no respect for you Right?
She isn't going to for quite some time yet. No matter how much you do right her mom (real mom) is always going to be right and you are wrong. Don't take it personal remember she is dealing with a lot. Try to put your self in her shoes you know the old saying you get more flys with sugar then vinegar...true true true. Be sweet to her and be understanding of her position and tell her that you are not trying to take the place of her mom you are just trying to be her friend and help her make her life the best it can be.
Ask her what her expectations of you are and let her know what your are of her and work it out together. You will get a lot further with her if she thinks you are on her side. Let her see how you help her. At the same time let her know that you love her dad and you are not going to stand by and watch anyone hurt him the way she is hurting him...
Your position is a difficult one...but it can be dealt with
2nd....I hope you take this advice it will do wonders for your whole house hold....As a fosterparent I have had lots of trainings on how to deal with children and there problems and the best training I have ever attended is called Parenting with Love and Logic.
There are lots of books and videos on the subject. Go to the library and look up all you can on it. Love and Logic works... It works with all kids..it teaches parents how to offer choices they can live with and with you having so many young children headed into teen years you are going to need it.
3rd
Don't let your son get lost in the mix...Sometimes when we are stuggling with one child they get all of the attention and the others get pushed out of the picture... be sure to balance your time....You chose how much time you spend on troublesome issues and how much time you spend on happy issues. Kids learn that if you get more attention for the good things then that is where they want to be....again its all in the love and logic. Trust me you won't regret it...If you need more info feel free to contact me by email at ____@____.com problems are so familiar to me and I would be very happy to help you in anyway I can. Good luck Hugs M.