It really wouldn't be a good idea to consistently shoot on a 9/15 schedule. You would be guessing about dosage constantly (is she sure at her lowest point in the cycle? should I shoot less but it won't last as long - those kinds of questions.) In general, we consider a late shot a dose decrease and an early shot a dose increase and she would be getting a decrease and increase every cycle. And she would likely be lower in the pm (maybe too low to shoot) and higher in the am which would feel like a roller coaster.
It is possible to move the evening shot back if that would help as she is lower in the pm. (if that pattern continues) Several PZI users have done the 11/13 schedule. What time would be ideal that is close to a 12/12 or 11/13 schedule? For example, if you need to be asleep by 7:30pm, what is the earliest you could shoot the next morning? We can brainstorm possibilities.
PS. How about buying some sturdy child proof locks for the cabinet you are going to keep the contraband in?