easy, tease her, poke fun at her claiming she's "nosey"
she'll wonder why you didn't give a straight answer, this helps create sexual tension, it will make her wonder "huh, does he like me or is he messing with me? why wouldn't he like me? i'm great! let me try flirting with him some more etc. etc."
sadly if you didn't respond or gave a total wuss answer, i.e. "actually crushing on you", you blew it; which isn't a bad thing, mind you. You just learned from your mistake. With girls, it's never wise to be COMPLETELY open early on. Develop a mystery around yourself, but a mystery a girl would like to know. Hence, be charming in your own way (making cocky jokes, read a lot, etc).
Saying how you feel is a one way ticket to see-you-later-ville. A place I have personally been to many a time. But after much experience for the past 7 years, best advice I can give you is be yourself (but don't let her know ALL about you all at once). Sucker her in, tease her, MAKE her want YOU, MAKE her attracted to YOU
Check out this guy named David DeAngelo online, he's got great dating advice, it's worked for me!