Sorry to hear that you lost one of your girls. When a mink got into one of my coops and killed three hens, then returned the next day to take out a runner duck drake, I got so paranoid that I was afraid not only to free range, but to even go to bed at night for fear the killer would return. I left my windows open in the dead of an Iowa winter and slept on the sofa so I could hear any disturbance.
Eventually, I started to relax more, installed a lot more hardware cloth, worked much harder NOT to forget to close every coop door every time, and started letting the poultry out to free range again. But, I am almost always at home and can see what's going on all the time. I hope you find a way for them to be safe and you to feel that they're safe again.