Advice for argumentative and aggressive 6 yr old with HF austim

Hi, I'm new to this and need some help. My daughter is on the waiting list for high functioning ASD support but I'm really struggling with her behaviour. When out, she is gregarious, social and well mannered but at home. I struggle to maintain any control. She will refuse to do anything I ask, will lash out if I try to start her bed time routine and will argue with everything. My mum visits and she is very nasty to her nan, calls her names, won't look or talk to her. 

I've always tried to appeal to her empathetic side but I realise now she doesn't have one. I try to implement a routine but she fights it, and she sees her dad fortnightly and he won't follow it so it goes to pot when she's back. What do I do? It's getting worse by the day.