Because, as Betty said, George is filing an appeal.
Prosecutors are always involved when their Cases are appealed. They file briefs in regards to why the appeal shouldn't be granted. Basically they fight the appeal.
So on top of this Canepa is a busy special prosecutor because she still has Billy's trial and Jake and Angela's testimony in his trial, and then Jake and Angela's sentencing, then Billy's sentencing if found guilty, then Billy's appeals if he is found guilty. I would expect Billy to appeal.
Good for her, I wish her well as she fights for justice for the Rhodens, Gilleys and Manleys.