She would not have given up easily since she discovered possible food in the way of your eggs and chicks. If you have seen baby snakes nearby, they will come around as soon as they are large enough to eat your potential food sources. Idk if you have seen evidence of rodent activity. Some people say if a person sees a rat snake around their coop, it means they have a rodent problem. (A black snake is considered to be a rat snake variety.) That may or may not be true. Only twice have I ever seen a rat inside my coops, and it was during winter when snakes were dormant. And it was only one rat both times. I live in a rural wooded area, and snakes are abundant. If you live in a similiar area, you will always see snakes around your coop. If not, it may be that rodents are coming to your compost pile, and snakes are tracking them by smell. But an egg or confined chick is much easier to catch than a rodent, and neither will bite a snake. Meaning a rat snake will almost always choose to eat an egg or bird over a rodent. They eat adult wild birds, chicks and eggs too. Here is info about black snakes that will help answer your question(s).
https://en.wikipedia.org/wiki/Pantherophis_obsoletus
