Having to deal with bullies will NOT make your child stronger. It will make her a permanent victim, she'll become agitated on school morning, start being sick with fear, and will come to hate school days. This bullying must be dealt with even if, in the long run, it means changing her school. (That should be a last resort though).
My son was bullied (by a male teacher). It became so bad that he was being sick every morning from Mon - Fri but was fine at weekends. I eventually got out of my son the reason for him always feeling sick on those days and saw the headmistress. She agreed to move our son to another class and he flourished.
It isn't only children who can be bullies, it can be teaching staff, a caretaker, other children's parents etc. Bullying should never be allowed but we cannot always deal with it. If moving school is the only way that must be done but tell the staff what is happening first and only threaten moving your child if they will not co-operate.