Learn from your mistake. Next time someone is dumb enough to ask you if you like them (I'm assuming that's what she asked) and you DO like them then why not just say that you find them quite intriguing and would like to get to know them further in a less professional manner. That way if they turn you down then you'll not have creeped them out.
She sounds rather effed up if she was stupid enough to ask you if you liked her instead of just being cold to your pursuit. If she didn't like you back or didn't think dating a coworker was a good idea.
What exactly did she say that made you think it would be a good idea to tell her "how you felt about her" after not even having dated her proper? Or DID you date her proper and will come in after the fact to tell us that too?
I don't know what that means, does it mean that she is not interested and this topic should not be breached because we work together or does she not know where she sits with this or is she possibly interested but is scared of the potential fall out? I don't know where to go from here.
I think you need to ask HER those things.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion