I know the frustration you are going through. I have two male Yorkies 1 year old and at first this went on all the time. They need constant supervision when that small and a lot of patience. I posted my frustration with agression and received a lot of tips from various people. I have tried some and believe me it is working. We still have the tiffs but I had to let them know who was boss..... and didn't realize that is where I was failing. I was ready to sell one of mine, but things are working out great now and all I have left to work on is the one that pulls his hair out of his paw when he doesn't have anything to do...... That is getting better tooo...... Don't put your doggie on ebay just yet. Give it time. Maybe I need your puppy to keep my two straight, sounds like she is my answer
........... Hang in there.