I know she is somewhere on the map randomly doe 12 hours at a time. Is it 12 hours per day/week/month? How do I know where to find her?

I don't think there's a set timing when/how many times she appears, just that if she does, she stays for 12 hours. There's also a ping group (hashtag hydrus) you can join which will be pinged if she appears. And you really can't miss her, she'll be seen over the current world map, in a big whirlpool.

- The graphic was my biggest question, thank you!