Also great advice, thanks.
I spoke with her last night, but didn't have the courage to quite ask her out. Your words did help me to try to get a little more personal, though; she's a very private person, and doesn't let people know what's going on easily. I'm going to work up to it over a few more conversations.
I also reiterated my poly status, just so that would be in her mind and that my motives might be other than just friends, so she's not taken totally by surprise.