When is it okay to hug someone?
Hugging seems to be an odd social behaviour.
I know personally, if someone were to come up to me and randomly hug me, i'd tell them to get the f*** off me (but i'm also a 26 year old man, and I don't think men hugging other men is considered usually considered socially acceptable).
For you though, sounds as if shes fine with hugs. Does she know you have an ASD? (in other words, if she does, perhaps say '[name] I really want to give you a hug because [insert reason], but I feel kind of awkward (then either wait for a response, or ask if its ok)
If she doesn't know ytou have an ASD, and you don't wish to share that info, I guess it comes down to whats more important to you?
Feeling 'paranoid' that your hugging her will be misconstrued? or
Caring so much about her that you want to share the 'emotion' of hugging with her? If this is the case then it can't hurt to just ask if its ok to hug her. If as you say all her friends hug her anyways, i'm sure it'd be fine.
I could be TOTALLY wrong though, as I don't hug people, nor do I want to be hugged (unless theres a damned good reason)
Just do whatevers most comfortable to you, if you know its something your going to dwell on/bother you, don't do it, if you feel fine asking, or just hugging, I say go for it (just don't hug me without asking lol, jk)