B.C.
I don't think mood rings/jewelry are ever meant to be long term jewelry.
Even if you treat it with the utmost care, the color changing stuff wears out eventually.
Don't worry about it, or try to fix it, or replace it.
Your daughter will learn not to wear stuff like that in the pool.
She'll learn about consequences and she'll be more careful next time around (hopefully - it might take a few ruined things before it sinks in).