Advice needed on getting my daughter back into school.

My daughter is 13 and has stopped attending school as she finds it too traumatic. She's afraid of the 'people' as she puts it - ie what they think of her. She's highly sensitive and highly intelligent and a great artist (has been drawing amazing pictures since she was 2). She's convinced she is useless at everything - against all the evidence to the contrary, and she is really shy. She's suffered from bullying - mostly between the age of 4 and 9 in junior school, but now is very vulnerable and sensitive to everything that is said to her. We've been told to get help from a psychologist, but I want to have a better idea about sensitive and gifted kids before we go. People have suggested autism or aspergers, but I don't think that's it, as she'd pretty normal at home (if a bit volatile), but shy outside the home. All the indications seem to lead to heightened sensitivity as far as I can tell. She has an older brother who is highly intelligent and mature for his age (17) who had bullying problems when he was little, but if fine now, and a younger sister (11)who is very outgoing.