One possible plot could be that Black Cat is on a heist in a place where Dr. Octavius also has an interest. His tentacles might squeeze her as a way to stop her from getting to a valuable item first. This could lead to a power struggle between them where Black Cat uses her agility and thieving skills to try and escape the grip of the tentacles.
Yes, Nancy Drew can be considered realistic fiction as it often involves situations and characters that could exist in real life, with some elements of mystery and adventure.
Nancy Mulligan has elements inspired by real life, but it's not a completely factual account. Songwriters often blend reality with imagination to create a compelling narrative.
Nancy Drew is definitely fiction. The adventures and cases she solves are all created by the author's imagination. It's not based on real events or people.