Dog Trainer And No Luck?

I was a dog trainer and I have much experience with dogs, however my eight month old yorkie papillon mix does like to forget the rules of the house. At 8 months this behavior is unacceptable. She knows what she has done, and rather than scratching at the door she does it after she has made the boo boo. Her face is soo sad and I feel bad that I have to punish her because she knows what she did, but I have to in order to be consistant. Paper training is out of the question, she needs to be able to communicate potty time without going back steps. If the door is open she has no problem, just when it is closed. HELP!!!