ASD child school issues

Hello everyone 

I really need advice as I am totally confused, heartbroken and going through turmoil about how unfair life is to my little boy. So he is in year 1 now, last year at school was with lots of up and down.

Now he has managed to make couple of friends but one friend he calls his best friend (I know that boy doesn't consider himself his BF). He was friendly and nice to my son throughout reception but and been to our house for playdates. But his mother isn't fond of this friendship. She always tries to ignore me and my son. Would talk very nicely and will go over the top with other mums and their kids s but always looks down on my son. She doesn't mind sending him over our place for playdate but that's it. I find really hard to communicate with her and feel insulted the way she talks. She would look away or completely ignore me.

If it was not about my son I would have never let anyone compromise with my self respect. But knowing how hard it is for my child to make another friend and he (being so sensitive) won't be able to forget his friend. 

I don't know what to do. My son is asking as school has started to arrange for a playdate but I m dying inside knowing she would read my message and not reply. 

What shall I do?