Honour May "Hangover Pills"

You went out last night and got absolutely smashed... You go downstairs to get something for the hangover when you bump into your sister who suggests taking some of your dad's hangover pills... Half an hour later you realize that they weren't "hangover pills" they were viagra! Now you're stood in front of your sister with a raging hard boner! She feels bad that she got you to naively take the pills and wants to help you out...