Step relationships are challenging but you have a particularly difficult situation to deal with. But, then again, you do have a few advantages that other stepmothers don't have. For one thing, the real mother is out of the day-to-day picture which means she cannot undermine your marriage or mother-daughter relationship. Believe me, if she were in the picture, she could make things so much worse. But she is gone.
The hard part is that this is traumatic for your little stepdaughter. Her mother abandoned her, took her little brother and who knows if she inflicted any emotional/verbal/physical abuse since the state had to swoop in and take custody away from biological mother. What has that poor child been through?
Of course, the little girl is going to direct her anger at you. You're the one who is available for kicking around. You're the one who replaced her mother. Perhaps in her young mind, she might blame you for taking her mother's place.
In any case, what can you do? You can run the other way because it will be easier, for sure. Or, if you really love your fiance, you can fall in love with this precious, poor little girl. How? Well, there is a technique called "re-parenting" the child who lacked proper bonding and parenting at a young age.
You must treat her like your own child. Not his, not hers. But yours. If she were really your child, she would have had the benefit of feeling your hold her in your arms, hugging and kissing her, stroking her hair, talking softly to her to teach her about proper behavior (not scolding and threatening). A real mother is patient with her child and loves her child no matter what the behavior is.
A child acts out from insecurity and fear and anger. You can hold her close, look into her eyes and tell her, "I'm here for you. I love you and I will not leave you."
Do things to have fun together. They don't have to be big things but just everyday things like combing her hair, shopping for a new dress, getting an ice cream, singing and dancing in the kitchen, making each other laugh, tickle fights. Every day mommy stuff. Do nice things for her because that is what a loving mother does. Not just the scolding and disciplining.
Instead of looking angry or disapproving, look sad or disappointed. And when she does behave properly but sure to note that and provide positive feedback and encouragement. Too many kids only get the negative with no incentive to behave properly. When she misbehaves, take the time to tell and show her the better way to behave. Some kids don't know what else to do and need to be taught. "When you're angry, throwing things will not get you what you want. You need to use your words and tell us what you want."
Re-parenting begins--well, you can't put her in your womb so you start with the next best thing--when you cuddle her and hold her close a lot. If she regresses, let her because she will move through the stages quickly if you don't try to repress her. Ignore the baby talk but do say, "I can't understand you so until you tell me clearly, I can't give you what you want."
Think of her as your own little girl whom you found again after seven years. How would you re-parent her? With a lot of love, I'll bet. She really needs you, a mother who will love her unconditionally and not abandon her.
I know she needs structure and discipline, but before you step in those areas, you need to build a relationship with her first. It's like drawing money out of a bank account. You have to have some deposits put in first. The deposits are the love, trust and happy times together. Then, you can provide guidance and discipline because she will have learned to love and trust you and know that your discipline is meant for her own good and not a power play on your part.
It's not easy but it will be worth it. Good luck!
