I would definitely talk to the school counselors. Be assertive. The education system is responsible for your child's education and physical and emotional health. If there is a problem that is affecting your child's enjoyment of school--the school should be made aware of it. Let them know that you expect something to be done and if no action is taken you will hold them responsible if any harm comes to your child. Be calm, but firm. Also, I know that your daughter is afraid of this girl (and probably has every right to be) but when confronted with a bully, you have to look "brave" and confront them. Calmly and boldly tell the bully to stay away and that you will not be bullied into doing everything they want. Get other friends to help be supportive.
Here is something I found online that might be helpful also.
What to Do About Bullying
Bullying can be a big pain, but you don't have to let bullying get the best of you and your buddies. Here are some things to try if you're bothered by a bully:
Act brave. When you're scared of another person, you're probably not feeling your bravest. But sometimes just acting brave is enough to stop a bully. If you walk by as though you're not afraid and hold your head high, a bully may be less likely to give you trouble.
Ignore a bully. Simply ignoring a bully's threats and walking away robs the bully of his or her fun. Bullies want a big reaction to their teasing and meanness. Acting as if you don't notice and don't care is like giving no reaction at all, and this just might stop a bully's behavior.
Stand up for yourself. Kids can stand up for themselves with words by telling the bully to stop it, and then walk away. Kids also can stand up for each other by telling a bully to stop teasing or scaring someone else, and then walk away together.
Tell an adult. If you are being bullied, it's very important to tell an adult. Teachers, principals, parents, and lunchroom helpers at school can all help to stop bullying.
Be a buddy. Kids who are being bullied can use the buddy system. Make a plan to walk with a friend or two on the way to school or recess or lunch or wherever you think you might meet the bully. Offer to do the same for a friend who's having trouble with a bully.
Don't bully back. Don't hit, kick, or push back to deal with someone bullying you or your friends. Fighting back just satisfies a bully and it's dangerous, too, because someone could get hurt. It's best to stay with others, stay safe, and get help from an adult.