Aggression

I just became part of the chat today. Reason being is I need advice please. I live with a man who has two beautiful Pitts. One is name Ruger and the other is Libby. They are both rescues. Libby was rescued when she was less than one year old and has lived with us for about a year and a half. Ruger was rescued when he was two and is now six. Libby is my problem child. She eats the furniture, has no manners and now she has started to be aggressive. In November my beautiful daughter became the proud owner of a Bishon/Yorkie mix puppy, Vivian! Viv was only 8 weeks old when we got her. At first the dogs were good. Neither of the Pitts were overly excited about a puppy, but, neither of them were aggressive. Libby was even mothering Vivian for a while. Then something happened over the last four weeks. Libby has attacked Vivian three times. The first time was for no apparent reason and was snatch and grab then release instance. The next time she attached Vivian is was next to where we keep the food. Not feeding time. Just in the same area. This last time was triggered by nothing and Libby drew blood this time. I'm not sure what has tripped her trigger to become aggressive towards Vivian but I'm not scared to death for all of us. Libby has become outwardly aggressive to me in the last month as well. She hasn't acted on it, but, she has growled nastily towards me and it's caused me to be question her now. I'm not confident with her and I know that will lead to more problems. What do I do? Can this be fixed?

Aggression