I get it; I ran into the same problem. All you have to do is buy energy drinks and consume them while you're with her. To give you an idea, your stamina level determines how much "charge" the camera has for the nighttime sections.
The woman who sells potion ingredients left to deliver the Lust Potion and told me she would be away for a while, but two weeks (in-game time) have already passed and she still hasn't returned. Do I have to wait for version 2.3?
