Did you ask multiple times? This sounds like what could easily happen when someone won't take the initial "no," implicit or not, for an answer. Based on the rest of your comment, I expect so.
A few important points:
1. Repeated asking has been held to be sexual harassment, if repeated for long enough.
2. Here's a simple rule: ask once, and only once. She knows where you work. If she's interested, she'll ask for a rain check and get back to you.
> I just don't think this is suitable verbal behavior for supposedly rational adults
3. Rational adults understand and respond to signalling. They don't demand that all communication happen explicitly and on their terms, because they know that such demands are ineffective for all purposes, will not be heeded, and might make them social pariahs.