This app was mentioned in 1 comment, with an average of 4.00 upvotes
After you load it, immediately disable notifications for everything but "before period." I tend to prefer 3 days on that. To use it, just hit the circle on the start screen, select the day she starts, click on one of the flows (which sets it as having started) and that's about it. No real need to track the moods/flow or any extra shit. You're just wanting a heads-up on when she is due.