Multiple Sclerosis effects?

Currently I am seeing someone who has Multiple Sclerosis. I just went out with her a couple of times but it seems sometimes that when I say something, she just sits there and smiles at me with those eyes but doesnt seem to understand my question. I always wondered about this and when today when she told me she has Multiple Sclerosis, it all started to make sense. .Its only been a few months since I know her but she didnt tell me about her Multiple Sclerosis till yesterday. She was very shy, almost secretive when she told me about it. She said it was a huge secret and Im one of the few people in her life who will know about it. I also feel that she tries her best to be positive and smile…I havent laughed so hard or had so much with anyone else ive been with. but sometimes I feel that she is hiding this huge sadness inside her. She doesnt talk about it but there is definitely something there.. She does take a weekly avonex injection.

But yeah my main question is about the confusion bit. I would like to know if Multiple Sclerosis is the reason she just sits there sometimes, smiling at me, seemingly not understanding my question.