Another method of doing it would be to have a switch on the pill holder, when she opens it it remembers she opened it, and if she opens it twice in too short a period it tells her no
(sorry you got me thinking :P)
Possible situations with your method: She takes but forgets to swipe
Possible situations with my method: She opens, but doesn't take, then later opens to take but it tells her she took it
Another solution: She has to swipe to open the bottle, but still if she doesn't take it, then she can't even say "Well, I didn't take it before"
Again, got me thinkin a bit too hard 