So with one of the dancers, I'm going to track it anyways because there is a clear difference in mileage when she's ovulating versus when her period starts and she's admitted to me that her behavior towards me in the past was due to massive PMS. I've got the next 6 months planned out.
Should I allow her to know I'm doing this? And if not, is there a good way to get periodic updates about her menses without making her suspicious?


Inform her? Probably not. But your reasoning seems practical and without ill-intent.
There are apps out there that make tracking easier, with “ovulation predicting”
medicalnewstoday.com
The main thing I question is how easy it is to get “data points.” How frequent of a regular are you?