Can egg bound kill chickens

It does not need to. You can help her if you are not squeamish.

The hen must be in a safe warm, quiet area away from the other hens. If you have help, have someone hold the hen with her vent facing you and liberally but very carefully spread Vaseline or other similar produce around and inside her vent. This must be done with care as you do not want to break the egg inside her. Let her rest and she will lay the egg within a few hours or overnight. Watch this hen for more egg binding as she will be prone to doing this over and over.