This is tough! We too lost two different hens to hawks! One just bludgeoned our white Silkie Bantam to death, and we went out and chased the hawk away! However, the hawks come back and we can see them flying overhead! We also lost our black Silkie nearly a year later, and aren't sure if it was taken by a hawk, but do suspect one. Silkies are easy prey, for sure!
In addressing your exact situation however it appears your hens are doing what they feel most comfortable and safe with doing by hiding...but it seems as if they are hiding from the enemy and need some type of truly safe zone!
Unfortunately, we have resorted to a very secure wire run attached to their coop for nearly every day use. It allows them to go outside every day and feel safe all the time, no matter what comes in our yard! (and we do have MANY predators in our yard-from hawks, owls, coyotes, foxes, raccoons, neighbor dogs---and who knows what else...!) We do bring in fresh cuttings of what is outside for them as often as possible, and they LOVE this! Grass cuttings, weeds, not to mention with Autumn now here piles of Fresh leaves that they LOVE to thrash around in....!
Even yet, we often still feel bad about having them,
locked in, but do feel more conformtable as we can't watch them every single minute! Even when we have, we still lost our 2nd chicken, and it happened extremely QUICK!
I have read on different forums ways others have attempted this, with varying success rates of course...but you still have to do what you feel works best.
I am so sorry you lost your sweet hen, it seems they do find the sweet ones and it is so unfair! Sorry, I feel your pain!
Also, I understand your other hens fears! Ours reacted the same way, and that is good!!! but it makes you feel sad, as who wants to live in FEAR! Ugh! So sorry!
Give us an update and let us know what you figure out!
Hugs!