I don't know a lot about it, but I had a similar experience with a Telescopus annulatus (African Tiger Snake). The species is quite a bit smaller than a Corn. She started continually cycling with no male. She eventually prolapsed an oviduct. At first the vet tried to stitch to prevent her from doing so again, but that didn't work, so then he spayed her. Unfortunately, she passed a couple days later.

I had a Baron's Racer that would lay slugs annually without the presence of a male. She eventually had an infertile egg unshell itself inside her and ended up going septic and dying. I didn't know what had happened at first. She developed an eye infection, which is why I brought her in. I was given antibiotics for her, but she only lived another day, and passed the unshelled egg; which explained it all.  I only share that because sooner or later, as I'm sure you are concerned about, something is bound to happen during the laying process. I think it'd be worth consulting with a vet and asking about the cost and going from there.

The only other thing I can think of is trying to get her to stop cycling by changing the temps up a little or something to make the conditions less favorable for breeding (even though I know you're not pairing her). I hope you get where I'm going there. Do you currently brumate her?

When I retired her I stopped brumating her since I wanted her to eat through winter and bring weight up. It's been like that for a number of years now. I do keep her a little lower in temperature than most trying to keep her from getting excited. There is the normal hot spot but the house temperature she's in is 68 degrees f normally. Everyone else is between 70-72 with hot spots as well. This spring and summer so far actually is the first year she hasn't laid anything. So I hope that continues. I was just curious who may have had spaying done or not and their experiences. I'm really glad you answered though I'm sorry your girls didn't make it. That kind of scare is the reason I want to look up options.