I'm beginning to notice that in some posts above I've been painted as someone who is somehow directing my Dd not to play with any child who had SN. This isn't true. I make no suggestions at all about who my DD plays with. She chooses her own friends and I choose mine.
I suppose it's difficult to be rational when there are complex and emotive issues about the socialisation of children, but let me say again - I don't choose my DDs friends for her, and any playdates she has are based on her preferences, even though sometimes I'm not overly fond of the child's parents.
It so happens at this time my DD has no friends who have SN. My DD was monopolised last year by a girl who has Aspergers and the school was very good and got all the girls to mix after it appeared my DD was being bullied and monopolised - this isn't a SN issue - it's a socialisation issue. I don't feel sorry about my DD expressing her preference in her friends: she's a child herself and is learning what she likes and what she dislikes, and she's not magically mature just because she's NT.
For sure I'll explain why her classmates are talking nonstop in her face about their collections of stickers/ juice cartons / whatever (as one particular boy does), flapping their hands /knocking things over/ shouting/ helping themselves to her stuff/ and scribbling on her books, but at the end of the day, my DD is friends with girls who are not doing these things.
At the moment my DD prefers to play role play games, and especially imaginative / magical games, with complex story-lines and characterisations, with girls who like these sorts of fluid and creative games.
The school is very inclusive and encourages group activities in class and every child is valued. About a quarter of my DDs class have learning difficulties/aspergers. There are three support teachers assigned to her class, as well as the class teacher. I's a very inclusive school, and they are sensitive to every childs' needs.
Most of the mums whom I like happen to like have kids who have SN, and we go out and have a laugh without any kids at all - we tried the other way - meeting with kids - but nobody had a good time, so we leave kids at home now, and have adult conversations
after the watershed.
I suggest to the OP that if she wants to support her friend, she see her without any kids at all, and have a laugh with her, and if this can't be done, then have the boys play where they can be seen and impose boundaries as you would any other playdate time with any other child.