I've often wondered why some animals, or people, have the problem, when others do not. I know that there are a lot of factors, but still...
Ananda the cat was spayed the same day as her siblings, and she had the same problem as Chelsea, while none of the others did.
If you took Missy in on the original day, would they remove hers?
You made the best choice. Please keep us updated on how it's going.
Love All Life, Thank You For Posting! :)