Schedule a conference with the teacher that includes your daughter. Making her a participant in solving the problem is essential. At the start of the conference, the purpose of short term study periods at school must be explained to your child. She needs to understand that teachers give students this time to organize their work and to clarify what needs to be done for homework. The students are able to ask questions about assignments and get any special help that is needed. It should also be pointed out that if she learns how to use this time effectively now, she will be able to reduce her homework time in high school considerably, leaving more time for her activities.
After the discussion of the purpose of a study time, the teacher needs to restate how she expects your daughter and the other students to behave during this time. Then the ball is in your daughter's court. She needs to tell how she is going to improve her behavior. You want solid suggestions -- not promises to do better. If she has no ideas, you could suggest the following: seating her away from friends, using a study carrel (a partition used for private study) in the classroom, seating her away from all her classmates in the back of the room, and having the teacher give her one reminder not to talk.
These suggestions may not be sufficient to change your daughter's behavior. It may be necessary for her and the teacher to agree on an immediate consequence any time your daughter fails to behave appropriately in class. Finally, both you and the teacher should remember to praise your daughter as she begins to resolve this situation.