I don't think it's about a particular person, but if anyone would care to share about any of Morrissey's real-life friendships or acquaintances with disabled persons, I would be very interested.
I think it follows a theme found in many other Morrissey songs. The lyrics mostly give an outsider's perspective of a disabled person confined to a wheelchair who, from their point of view, is a "monster" who can only dream of being loved. At other times, the lyrics present the perspective of the girl herself--"Jesus save me from pity, sympathy, and idiots discussing me."