Disclaimer
I am going to be brutally honest with you
I have a friend with a ds who is having exactly the same issues and unfortunately her ds carries out his agression on my dd.
He hits her, bites, pushes,pulls her hair at playdates and at nursery school.
His mother "in my very humble opinion" is far too soft with him. He never has consequences followed through, she tells him off in a too soft voice, and does not instil basic manners in him. She allows him to hit her and speak to her like shit.
He is not a pleasure to be around, and I now avoid meeting up with her as my dd is always physically hurt when she is his presence.
A number of other mums who this little boy has been agressive with, have all thought the same thing that she is too soft with him. and unfortunatley this little boy is now labeled as the "naughty child" which is a real shame as I know he is capable of being a sweet loving boy.
I dont think the mum is doing him any favours by not disciplining him in an effective way.
I really feel for you as I can imagine it is very very hard for you, but please please reflect on your discipline methods and be honest about them and perhaps ask yourself if they are effective.
Follow through with your threats
Get down on her level and speak to her in a loud tone "no we do not hit"
Punish the behaviour - no sweets, tv programme, take her home.
You will probably hate this posting, but I wish I had the balls to say to my friend what I am saying to you, and stop this little boy getting a label