OP, no one is saying that you have it easy. Of course you don't, and you are entitled to your feelings of frustration. However, YOU chose that life and as such, you are now dealing with the consequences of the choices you made for yourself because you believe the outcome would be worth it.
This child had no choice but to accept a new life with an outcome that is not the one she would want. So not only she has nothing to gain from the life that has been thrown at her, but she is still a child, with less experience in resilience that would be expected from an adult.
It's possible to have sympathy for you, but a lot more for the child and when posters start referring to children, whether directly or their behaviour with such attributes as 'monster', then it's hard not to react.
You still have the option to walk away from the situation, so doesn't, or at least not without losing her dad, someone who was there for her every day before. Surely it's not that hard to feel some empathy for the child and respect that it might take her a bit longer to accept that you are not the cause of her life being thrown apart.