Hi. Congrats on your first Yorkie. Making yapping sound didn't work for me either. I even mimicked the way he whines to let him know that I didn't like it. He just looked at me as if saying, "oh this is no fun to you? It sure is fun to me." Lol.
Anyway what worked for me was to take him to a (puppyproofed) room with nothing interesting at all. He soon learnt that biting gets him to the sad, bland room and behaving nicely gets him cottage cheese or liver treats or play time. Also try to freeze some chicken broth and give it to her to soothe her teeth. Good luck, you'll need it
