Theory // V i c k y ::

"Sorry sexy, some secrets have to stay secrets.”

meaning - “to conquer, victory”. 
marks - met Mayfly Man online, unidentified description: “couldn’t tell; he had a mask on” … occupation: “maid”… ideal night out: “dungeon”… makeup: “whatever’s cheap”

Personal Headcanon: Mysterious online “Vicky” is actually Moriarty, toying with Sherlock. Her answers are just vague enough that they could be made up. No face-to-face meeting, done by instant messaging online. References to wearing a ‘mask’. Ideal night out would be a dungeon. Do not tell me Moriarty could not construct a female online identity and history.

Re-watch that scene.