My dog broke off her cord and pushed out through a gate left unlocked by some workers and bit a neighbors dog, am I responsible?

The woman never walks her dog on a leash and her dog runs up to my gate everyday. On this particular day some workers left my gate unlocked my dog broke her cord and just pushed out and chased the dog down. She ended up biting the dog and my boyfriend had to pull her off. The woman brought me her vet bill am I responsible for this bill?