I'm not going to help a girl with a disability
Why don't you want to help her?
She came to school with assistance. I want to get the same assistance when I get older.
You should help someone who is disabled because they can't help themselves. It's rude to not want to help a disabled person if they are in need of something that they can't do for themselves.
Can't the school staff help her? I've never heard of schools not helping their students.
It sounds like she has an assistant to help her. So she's probably okay. But if you do ever see her looking like she needs additional help, it's polite to ask if you can be of assistance.