Happy to hear she is swimming around.
My husband changes our water when it gets murky. I'd say its roughly every month or so. But if it gets dirty sooner he changes it sooner.
Waiting until the water is murky kind of means the filter has done all it can do (i.e., can't filter out the gunk)...and clear water does not always equate to healthy water.
It is amazing how much water affects their health.
Maybe consider getting on a regular schedule for *rinsing* the filter media so it, and the water, stay happy.