I vote for option 3. A lonely man searching for survivors in a post apocalyptic medieval world finds a maiden and saves her from a horrible monster. She decides to thank him in a very enthusiastic way.
“Maiden” means “never been married”. Are you expecting the young knight to marry her? If the appropriate reward is to lie with the knight, that might not change her status; I think we already know she’s not virgin.
How about Young Maiden get ravished by Tentacle Monster in Post Apocalyptic world and is rescued by Young Knight from rebuilt Fortress, who accepts her gracious reward? :) I know... it's been done to death, I'm sure.
If more people show interest then I'm definitely going for it. ;)