I am so sorry to hear that your daughter is being bullied and harassed by her peers. As you know, the victims of bullying suffer a great deal, and they are more likely than their non-bullied peers to report sadness, worry, and physical complaints (e.g., stomach aches). Therefore, it is a very serious problem that requires the attention of the school staff.
 
To help your daughter, carefully document each and every event of bullying. Write down when and where it occurred, what happened, and who was involved. Talk with the school principal about the school's anti-bullying policy. Make certain that they are following through with their documented policy. If they do not have one, educate the principal about the seriousness of bullying (and your daughter's situation) and work with the principal to create a policy. Let him/her know that you will be taking the issue to the district office if your daughter's situation is not managed better. If he/she continues to be unhelpful, take your documented evidence of bullying to the district office and demand that your daughter be better supported.
 
Some of what is required to better address the situation involves consequences for your daughter's bullies. It is important for you to know that meetings between the bully and victim have been shown to be not productive. Mediated meetings are only useful when the parties involved are "equal in power" and bullying involves an inequality in the power relationship.
 
For more information on the consequences of bullying and possible interventions, please see the following section of this site:
 
http://www.education.com/topic/school-bullying-teasing/
 
Best Wishes,
 
L. Compian, Ph.D.
Child Psychologist
Education.com