Last 5 or so hours gone. But you really should've known better than to tell her. Let her maim you a bit.

Agents allergic to asprin take Suebuprofen instead, and it's never been said exactly how that works, so she may be in the clear to take it as a substitute without suspension of disbelief getting in the way. She could also go for an Obliviate charm to forget you telling her, or some other memory-fuzzing technique from other canons (There's a trope page for Brain Bleach, if you don't mind far too many options and being distracted from your original purpose for hours on end).