Scott, when people ask me if there is anything further I could do I reply
'no, if there was I would have done it'
do you really think you can improve the worn area? if not don't get drawn into wasting your time on a pointless exercise, tell her you made the carpet look the best it will ever look and to keep working on it will cause further damage.
if you do go down and improve it what you are telling the customer is you didn't do the job right in the first place, is this the case? if you did your best then that's the end of it.
Mike