Amber,

It doesn't sound like you have much to worry about. Since you tested her for dehydration and her scruff went back to normal, it sounds like she's getting her water source from somewhere else. Since you have caught her drinking out of the toilet, I would make sure it's flushed and clean and you don't use any "bleach tablets" in the tank. This could be toxic.

How about putting a water bowl in the bathroom??? Unless she starts showing signs of not eating or using the litterbox, I wouldn't worry too much!