[yorkietalkjilly]

Look for the attacker's body language to change, which usually starts with the dog going stock still, silent, ears coming up to alert status or back flattened, eyes focusing intently and locked on the other dog, face tense, mouth slightly open or teeth bared, hackles raised(not many Yorkies can achieve this) or putting a paw up on the older dog, trying to mount her.....are all the body language indicators that one or all in combination can indicate your younger dog is about to escalate her behavior into aggression. All you have to do is stand up, say "No!", advance toward the dog and walk into her space - right into her body if she doesn't move at first, forcing her to turn and eventually give up and leave the area. Do this every time she begins to focus intently or make dominant or aggressive moves on the other dog and in time, she will begin to understand you have set boundaries of behavior she cannot cross and will immediately stop her improper behavior. In time, she will remember what is coming and begin to control her own aggressive behavior as she knows you will step in and back her off, forcing her to leave the area, which she will try to avoid to be able to stay with you.

Setting them up for success by taking up all chewies, toys or things they might have issues over until the younger dog is better trained about how not to react will probably keep them from conflicts over these things as well. They will have to enjoy chewies and toys one at a time with one in a crate or another room for a while.

There is more you can do if you want to train your younger dog to accept the other dog's right to exist and live her life if you want, if this problem somehow continues despite your standing the offender down each and every time.