Your stepsis tells you about her long hike and slowly takes off her stinky boots and stinky socks while smelling them herself and then having you smell them.  "I know why your still here even though my feet are free from my shoes and socks and absolutely STINK! It's because you have a foot fetish huh? You have a fetish for SMELLY feet especially! Come here and get close to my smelly feet. Come smell them! I know you LOVE sniffing them. How about you get a little lower on the ground now ? "