I am so very sorry this has happened. I feel desperately sorry for both mums involved. It is extremely important for us all on the outside to remember that the children are only 7 years old. Also at 7 and perhaps especially for girls, it can be very important age to have friends.
I have both taught this age group, then after changing career, done work with Autism and people on the AS.
I do hope the school is doing all it can for the child on the AS. Losing self-esteem now will be the beginning of a slippery slope. I feel so distressed for her mum too. No doubt life at home is no easy ride. This only child was probably longed for and perhaps long-awaited and then seems to have arrived with Autism type behaviour. This is agonising for parents, especially if their child was responsive and smiling as a baby then stopped being so at about two years, withdrawing and having tantrums, being distressed for no explainable reason. Her mum must feel pain when she sees other children hitting their mile stones, and other families with two or three children all doing well at school. Then her little one bites and hurts others and she has to explain all over again about AS...
Our OP has coped so well in this really difficult situation. How awful it must be to have your child physically hurt by another and then, when hurt again and pushed too far, how hard it is for our OP when her child retaliates against her attacker who is the Special Needs Child! The very child we are all supposed to give time and patience to! But do remember the bitten child is only 7. At seven she has already coped above and beyond and this is just too much.
These are just children and Mums' feelings are incredibly sensitive. All of us need to give them time and understanding and as much comfort as we can. I think the situation is one which time will heal so long as it is given time. Both little girls and both mums need a lot of love right now. Both have coped so well and neither deserves to be judged. There's absolutely nothing to discuss and definitely nothing to argue about. Nobody is in the wrong. Children get upset and act out. We deal with it and teach them love. Love is learned from experience.
I really do hope the two mums can become friends again. Start by deciding not to let the children come between you! Seeing their mums chatting and laughing together would be such a good example and encouragement for the little girls.
Please forgive me if I am saying the obvious. I am a Granny, the survivor of two Traumas, and have had a lot of things happen. I feel so much that I want to hug these two mums. The little girls just need to be given space and time, time to grow in confidence and lots of love . As time goes by I do hope they will be friends again.