how to handle a problem step child?

my stepdaughter is 5. I know that she has not suffered any personal trauma. she is in pre-k. she has done pretty violent things in her class to the point where NO other kids in the class will have ANYTHING to do with her. her teachers have told me that out of 20 kids in the class that there was one other kid in the class that would play with her and she was slapping and taunting this child but finally she punched this kid in the stomach and ran her over with a wheel barrow. she has stabbed kids with a fork, stuck a plastic knife in a kids ear, punched a kid in the eye with a block so severely that the teachers were worried it had damaged the child’s eye, she spits on kids, she hit an adult in the face, she kicks kids. she now has segregated herself to be completely alone from EVERYONE! and she doesn’t care. she never complains that no one will play with her. she seems perfectly content to play alone. she’s completely anti-social. she is the absolute darling of her father. her mother sees it, I see it, her teachers see it, everyone in the family sees it, but he refuses to see it. she says things like “when the fish dies can I scoop him out” this kid is not normal but her father thinks she’s just going through a phase. well unless it’s a life long phase, it’s not a phase. my husband is not listening to me. he gets very defensive if I say anything about her. he knows that her behavior at school is not normal, but the most he will say is that he hopes she grows out of it. she gives me dirty looks. I’ve been with her father since she was 2. so it’s not like we’re in a new relationship. she doesn’t like her mother either. the only person she likes is her father. unless you’re doing something for her right at the moment she doesn’t care for you. she is extremely manipulative, but it only works on her dad because everyone else is onto her. she pushed her 2 year old cousin down so hard on hardwood floor that he started coughing because he was getting added attention because he’s so young. I watched her do it and when I called her name she turned around and said “it was an accident” it clearly was no accident. she had already earlier that day hit him in the head with a plastic bat. I don’t know what to do about her without the help of her father. does anyone have any ideas?