This made be hard to hear, but although you are scared and worried, there is some good in the situation. The first is the dog defending/protecting/guarding her precious tennis ball did not do more damage than she did. It would have been different, and sadder if that dog had had malicious intent. Though poor Cassie is in pain, she is alive, and will get better.

The second is that the dog's owner was good enough to drive you guys to the emergency vet. Nuff said about that.

The best part, though, is that, despite her pain and discomfort, Cassie is home with you, where she can feel safe and secure. My family once lost a dog who was injured, but the vet said would recover, we are sure because of loneliness. She had to stay at the vet's, in a kennel by herself. She was a dog that was used to being with people most of the time, in an active household. At the vet's, she was alone. I'm sure they went in to change dressings, or give her food, but the vet's office was many miles from our house, and we couldn't be with her at night, either, after they closed the offices. She died, at the age of 5, from a herniated diaphragm (an non-life-threatening injury, we were told) - but we know that after several lonesome days and solitary nights, she gave up, and died of sadness. We never brought another animal to that vet again.

Be glad your little pugster is home with you, and give her a kiss (on a part that doesn't hurt) for all of us.