Just to go ahead and dispel a few things to make sure everyone after this is on the same page. Mites that are parasitic to rodents are not to reptiles and visa verse. is it possible that they might have hitchhiked on the rodent for a short time? Sure but snake mites don't survive long on warm blooded critters. It's just as possible that you picked them on your person and brought them in. I will say this the number of mites you're talking about sounds odd for a snake that only had them for 1 day. So from what I've known of snake mites..The animal had them for an extended period of time and they just got bad enough to make her soak herself. The fact that you said it was a "new" snake lends even more credence to the idea that the animal had them before you got her and they just now got bad..