That's funny that she cleaned out the bird bath for you (well, for herself). Really cute. My in-laws have a bird bath that gets so much attention too. Lots of little birds come and splash around. Then the bigger ones come and the little birds scatter. They make a lot of noise and it sounds like they are having a party outside.
I hear what you're saying about the dirty water but in the wild all bets are off I suppose. I saw pictures and videos of wild African Grey's (there's someone on the AG Facebook forum who is doing tours to their secret locations) and they were drinking some of the blackest and filthiest water you can imagine.