I don't know if that would be the case, with the drop rate I am seeing I am getting her drops all over the place. Rarely I will get her dropping right after I got her and other times there will be a massive gap in between drops. There is just a possibility like Eversor said the RNG could have just been that bad she may not have dropped because of it. The worst I have had was using 300 stamina and didn't get her once.
But who knows, I wouldn't be surprised if a tactic would work like that on an already hard and time consuming event.