Well, what is your sexual orientation?
You said you don't think you are meant for GGs, but you didn't say that you are attracted to men?
So are you straight, bi, or gay?
Is this a person you could come out to, meaning is there a risk she would tell everyone at work, and if she does would this impact you negatively (I don't know how "out" you are).
If you're not out at work and don't feel comfortable telling her just yet, you could simply answer her question. If you're interested in her and are also into men, you could just say you're bi. Or, if you're not into men, you could say you're hetero but you're not looking for a romantic relationship at the moment, so maybe the two of you could do things together and become friends. And then see where it goes.
Your last comment concerns me though .. the fact that you don't like to give in to your desire to date women because it makes you question yourself. Are you on your way to transition, and does experiencing an attraction to a GG bring out more male feelings in you than you would like? Or is it that you feel that seeing a GG would take time away from the CDing?