You know for a fact that she's into you, but you're asking how long you should wait before she shows you. Let me guess, you've heard from everyone and their mother that she's into you, but you're waiting to see it for yourself. Am I right?
Instead of waiting for her to 'spill her guts', pay attention to how she acts around you. Believe me, if she's into you, she'll let you know without saying a word. Better yet, flirt with 'her', see if she responds or pulls away.
Say something along those lines, and by u saying to her that u dig her takes away that fear from her of being "rejected" by you because now she KNOWS that u DO dig her too
wrong advise bro.
And one more thing, never play the 'waiting' game with any one girl, there are way to many options out there.