So glad your girls made it!!! Glad you understand dogs enough to realize that's just what they do sometimes. I really hate saying this... but if it were my dog (before she underwent aversion training!) they wouldn't have made it. That dog of mine killed a neighbor's chicken who came into our yard, and another one of mine who made it out of her yard. I worked on aversion training and now she's great around the chickens, but I would never trust her alone if I could help it. Her prey drive is extremely strong (pointer/staffordshire mix).
I was having an issue with a neighbor not long ago. Their dog HATES other animals. Killed one of her owner's cats, then kept trying to get into my yard to attack my dogs. She actually succeeded in getting into my yard three times - once while my dogs were inside the house (thankfully) and twice while my dogs were outside, but after we put up a double fence (thankfully! that second fence kept her from being able to reach our dogs). I was worried sick she'd get into my yard when I wasn't home and attack my chickens, horses, or goats. We kept talking to the neighbor about it, and all he ever did was put a chain on her, and then she'd slip her collar and dig into our yard again. He finally rehomed her (apparently it was his ex's dog, but when they broke up she left the dog behind... he isn't much of a dog person, prefers cats).