I would push for the school accepting responsibility for allowing the bullying to continue, apologising and putting a plan in place to stop the bullying.
They are failing both girls. Your DD who is miserable and anxious plus Anna who is learning behaviour that will not help her in later life.
The bullying needs to stop and a school can do this if there are proper methods of dealing with the problem behaviour.
For example, you can ask that the children are sat away from each other in the classroom, supervised properly at break etc and that Anna is told clearly that if she bullies, insults or physically harms anyone, that she will lose her breaks for a day.
The school need to be consistent with his until Anna understands the consequences of her actions. If Anna refuses to behave, then the school will realise that they have a bigger problem on their hands. I had this issue with my DC’s previous school. L
One of my DC was bullied at school and eventually a similar plan was put in place. It worked with the satellite bullies, but the main one just wouldn’t stop.
I pulled both DCs out of the school when the school stopped the supervision and didn’t put anything else in place. My DCs are happier at their new school and the bully’s reign of terror continues at their old one. He broke a girl’s arm in the class last term and is still there. The girl has left.
Interestingly, my DC say there is no bullying in their new school as the staff there are far tougher.