I'm so sorry for this happening. I've lost 2 to foxes, both around this time of April 3 and 4 years ago. Both times it was well before dusk and the fox(es) had to cover 100 yards of open ground to get to the chickens.we have stupid laws in UK. Once trapped it isn't technically a danger so it is illegal to shoot it. Thank you for the suggestion though
What are you allowed to do IF you trap it, donate it to the local fox hunting club? In many places, including the state I live in, it is illegal to re-home a predator off your property, no making it someone else's problem. No one here has enough land to legally move a fox far enough it won't come back.
Hopefully your current shock will subside and you, and your girl, can recover. It takes time for both the emotional and physical recovery. Do you have hot wire now? I think hot wire running over the top of a 4' fence will keep foxes from climbing over. Additional efforts are needed to keep them from digging under.
A problem with kill traps is they are not selective in what they trap. Could be your dog, cat, maybe even a chicken if it is inside the fence line.what about trapping? foot hold's work good in a dirt hole set if you know what your doing. you might need a trappers licences to set traps but if your good at it they work wonders.