My one dog is getting aggressive I am at a loss on how to stop it.

I have a 6 years old pug mollie. The last few months have been kind of hard with her. I have a 2 year old bulldog and 2 cats. Mollie has been chasing the cats when they walk into a room she is in. She even grower at Thor the my other dog yesterday because he got close to her. Any advice will be great if love my baby girl so much and this is not normal behavior.