Sometimes it doesn't pay to question things too closely. However, if your partner is more on the vanilla side - well - try to make cream soda! But how?
The obvious question right up there in the first batch is, "Why are you like this?", or similar. To which the response is inevitably, "I don't know." Yes, it's next to useless, and what's worse, it looks like you're keeping secrets. The 'hand caught in the cookie jar' look doesn't help, either. You can see one of two reactions galloping at you at high speed, can't you? Either: "Well, just tell me." or, "Well, if you're not going to communicate..." [walks off in a huff].
Head both these off at the pass, so to speak. Ask her to tell you her favourite colour. (If you don't already know.)(or confirm it.) Now the key question. "Why is that your favourite colour?" Obviously don't accept, "I like it the best." or other such subjective twaddle. It isn't possible to give a solid objective answer to something so subjective. I.e. something that is simply a question of taste.
[Never underestimate the power of twaddle! It is the only way to describe our likes and dislikes!]
Once you have your loved one in a floundering possition, ask, "Would you accept that kind of answer from me about chastity play?" Q.E.D. (quod erat demonstrandum - used in mathematical proofs, meaning - which was to have been proved.)
This is only a first step. Please don't force the pace. Give your loved one time to digest this. Tiny Steps. And remember, even after all the steps, they are free to choose not to play. They are individuals too!
Of course the fantasy...