I think you have your answer to why her behavior is what it is......if I were you, I would do as much reading as possible about Autism & the behaviors associated with it so that you can understand her better. It's normal for them to have a very narrow focus & only want to talk about that thing (movies in her case).

Reading & understanding more about what she is going through & what behaviors are NORMAL for her will help in your understanding. You may not choose to be close to her because of this. It took me 33 years in a marriage & 7 years after I left to finally realize that the guy I married was on the Autism spectrum. Great, understanding helped with my anger toward him....it didn't help me want to stay in the marriage but at least I finally understood what caused all the issues in the marriage.

There is a good book (you can probably get it from the library). The Complete Guide to Asperger's Syndrome by Tony Attwood. It not only covers information about adults who are on the spectrum but also about teenagers.

She does need help to learn skills to become able to function in social situations while it also helps for those around her to understand the way her thinking works. They can adapt some what, but mostly, their brain just works in a different way than ours & to have a close relationship with someone like that it takes understanding & the willingness (ability) to tolerate the behaviors that don't fit in with ours.....otherwise, the only solution is to keep a distance.

I always wondered why there was never any emotional connection in my marriage....I thought it was my fault until I learned more about what was normal for someone on the Autistic spectrum. Some people have an easier time getting along with them than others......we fought like cat & dog throughout the marriage because I didn't have the ability to tolerate his behavior after living with totally dysfunctional parents all my life....I was fed up by the time I got to my marriage.