In my opinion this is not normally the job of the biller. You are not a coder. Are they just asking you to do this for a few days? Weeks? Is it something you feel comfortable with? If it's temporary, and depending on my relationship with the MD, I may agree to spot check a couple, or watch the billing to see if the dxs match the service. But it they are expecting you to check her coding, that's a bit out of your scope as a biller.