That's up for the player to decide, whether the character in question is a PC or an NPC. The book is very careful to make that pretty clear:
Regardless of the results of the roll, however, each player still gets to decide how their character reacts. Being turned on by someone doesn't imply or demand a particular reaction.
That's why the player controlling the character affected by the
Turn Someone On Move gets to choose which of the three options happens on a 7-9 result; the mechanics never force a particular reaction. You're never forced to give in to someone's sexual advances, it's something you choose to do.
So, let's say Mara's character uses the
Turn Someone On Move on Catherine's character and get's a 7-9. If Catherine's player chooses the "give themselves to you" option, it's up to them to decide what that means for their character. It'll also be based on what Mara actually did in the fiction. Like if the two of them were sitting in class and Mara's player narrated a hair flip, a button adjustment that exposed just a bit too much skin, and then a hungry lingering stare, I doubt Catherine's player would have her tackle Mara and start a make out session right there on the classroom floor. Then again, the player might decide that's
exactly what Catherine would do. Maybe Catherine just passes Mara a note with a hastily scrawled "any time, anywhere" on it. She's giving herself to Mara, just at a later time.