Unless you have just started fourth grade, then you've been putting off asking her out for a hell of a lot longer than three weeks! (If you are just starting fourth grade, you are too young to date (except if you are perdix, but he was an exception))
You've probably put on this gay act to get close to her. Girls are rightfully suspicious of the motivations of straight guys, but often let their guard down to non-threatening gay ones.
Now, if you were clever, you'd tell her that she "straightened" you out ;)
(I hope this gets in before the inevitable dreaded "Comments are deactivated.")