Good Luck, but even if you are not successful remember that your little girl thinks of you as Dad.
My eldest (he is 26 now and he was 4 when his mum and I got together) is my step-son but as far as he is concerned I'm his Dad.
His Mum didn't want him to have any contact with his biological father, but I insisted he should have contact because I realised what a waster his dad was and that he would mess up. That is exactly what happened, in fact we made a point of keeping in touch with his Grand Parents who were lovely people and they used to treat me like family and praised us for being so good to their Grand Son.
When my step son was 18 he asked me if I would mind him changing his surname to mine, I was so proud !!
As far as I'm concerned I am his Dad and he is my Son and I would die for him just as I would for my other 2 children.
His real father was not his Dad, he was just a sperm donor.
So no matter what just continue loving and supporting your daughter, she and your wife/partner know who Dad is.