My neighbour in my tween years had autism (as do myself and my twin, however we’re much lower on the spectrum than the neighbour). To be “nice and neighbourly”, my mum would invite the neighbours over to parties etc. The autistic son would often touch our (me and female friends) shoulders, hair, etc while being near us and making odd comments. E.g, “I can see your bra strap a little bit” etc. Continuous askance from us girls and my mother to get him to stop led nowhere. Eventually, at yet another party, he sexually assaulted me.

NTA, autistic people do understand boundaries (I’m autistic myself and while I do struggle sometimes, I understand “no” and “stop” as well as any other person)