Do pursue this---tough but you will be glad you did in the end, take it one step at a time, break it down into doing, say, one particular piece of this work once or twice a week till it is done. You may have "caught" this T. And, my guess is she lied----I don't think it is easy to send insurance claims to the wrong address....it may even be done entirely online at this point.
You have every right to be furious!!!