"Guess."
(lame guess)
"You're not very good at this, are you? You can have one more go at the big prize."
If she doesn't guess it, leave her hanging "I'll tell you later, when I know you're not some kind of a weird stalker-chick"
or transfer to other material directly.. if she continues to prod, it's an IOI,
If she is really that interested She will have to demonstrate it.
And if you give it to her directly, without having other loose ends for her to paw at, you may have a bit of down-time in the convo.
(I have this theory that leaving unfinished stories can be a good thing, both as re-openers for you and her, and it leaves a bit of that mysterious shroud you should have. )
Giving her every bit of information for free will release all the tension.
That gave me an idea; I have to try this..
"That sort of information isn't free, you know." and make vague gesture towards your cheek/ear/whatever...
If she kisses your cheek, freak out "What was that, I meant you have to tell me something first"
or rub your fingers together as in "this is gonna cost ya"