I do not agree that her dogs should free roam either, that’s wrong and just asking for trouble. It’s their owner’s fault but dogs will be dogs and do not deserve to be killed for their instinct (just my opinion) They should be secure, as should your chickens.
First, I’m terribly sorry about your babies, I’m sure that’s very devastating. However, I have to agree with what @nuthatched says entirely..you need to secure your animals as well, such a delicate situation though. Good luck to you.