I've wondered if Cass is autistic for awhile now. A close friend has Asperger's and I've been around other autistic people and it really does explain Cass, especially being non-verbal and missing on social cues. While yes, her upbringing does explain that to a point, it should be possible for her to pick up on things quicker than she does...

Well, canonically, Cain's upbringing manifested itself as damage to the language center of her brain, preventing her from learning normally to read. So even if it's not capital-A autism, it's close enough for comics of the "X-Men equals homosexuality/superpowers equal puberty" meme. Get a writer to do some research, give her an all-age title, and I think she could even be the next big character. After all, the modern age of comics was begun based on characters that went through what their audience was going through...