Having been a stepmum, and also through personal friends, I have to say that daughters in particular, can be VERY reluctant to accept a new partner in either parent's life! I have also had female friends that absolutely refused to accept a father or mother's new partner, even when he/she had been widowed for more than ten years!
My late husband died in 2010 and my stepdaughter wages a campaign of war against me, which intensified after her father and I married. We had been going out together (but not living together) for nine years before we married. I received abusive phone calls, including threats of violence) whenever she thought her father was out. When he died, she came to our marital home with a removal van(together with several large and intimidating male friends) and stripped the house of everything that had belonged to her parents (which was almost everything except my clothes). These are just two examples of her behaviour. Her brother was OK. Neither came to visit their father if they could avoid it. Both were over 35 when we married. They had only lived in the marital home for a short time before their mother died (both were adults and living away from home at that time), I would have saved myself from a lot of heartache if I had not married my late husband. I had reservations, knowing how my "soon to be" stepdaughter felt, but I believed he needed my support. Never again!