Do you think I should force myself to bond with my boyfriend/fiance's daughter?
Do you think you would be a good mother to her?
I don't think I'm capable of raising his daughter because she is related to him
It is expected to be part of a child's life when you date the parent but you cannot force yourself. You will start to resent the child and it will be bad for you both.
Why can't I make her like me.
It sounds like you are trying your best, but sometimes a child will only start to feel comfortable around a new parent over some time. Be patient with her and treat her with love, and I think eventually his daughter will begin to warm up to you.