You have to make her trust you and you don't need to make her feel like she's not normal. Sometimes people do certain things with reasons that if we take time to know them, we'll know how best to help them.
It wouldn't be fair comparing her to other girls, she is her own kind of person, just get to know her and understand her better.
Try to make her comfortable around you and try to find out about her likes and dislikes, maybe it'll help. If she trusts you, she can tell you anything, including why she's being quiet, don't give up on her yet.
Jerryy
