I think my friend might be autistic or have aspergers syndrome. Are these the signs?

I'm not sure if she just doesn't want to listen to me when i try talk to her or she just has a really weak attention span. I don't think it's ADD because I have that along with OCD and I don't think I act all that strange. I know she she has autistic nieces and nephews, so maybe it's hereditary. Before she quit smoking weed she seemed more normal and able to follow a conversation then (I'm dead serious but I'm not saying it's right or wrong. That's was just my observation). Recently, I began noticing some strange personality traits. Not only does she appear to have a short attention span, she can't maintain eye contact, she mumbles and fidgets alot, she's usually introverted but when she speaks she says really random words/phrases that don't make any sense, and she has child-like interests. When she was a senior in highschool she hung out with freshmen that were really into the candy kid/rave scene and would act ten year olds. They would take ecstasy, but were against weed. I can't understand the logic in that (No offense to ravers. I'm sure there are some that don't act stupid). Another thing I noticed is that she can't seem to follow/understand conversations regarding philosophy or the meaning of life (but not everybody can I guess). She's been a pretty good friend for the most part, I'm just wondering if these could be signs of autism or if I'm just over-yzing her character.