One morning, for no apparent reason, blindfold her and lock her in your basement or in a room with no windows. Bring her the occasional morsel of food and small glass of water while you mindfuck her with your words:
“Our relationship dynamic has changed, starting today.”
By the time midnight arrives, she’ll really begin to wonder if she’s become your permanent sex-slave.
And when she begins to wonder that, you can be guaranteed she’ll be soaking wet.