I agree with Michelle. You should write a letter and drop the claims to paper and mail them in with the letter attached. Now, for the biller, she would have found her last paycheck as she was out the door. As for now, it is $950 that you know about. It may be worth it for you to get someone to do an audit of your claims.
Depending on your software, you may be able to run a report on services that have not bill filed, however, if your biller has not put the charges in, then this will not work.
Does your biller do in-house billing?