So, update:

Due to unforeseen circumstances regarding the friend she was planning on staying with for the holidays, our new friend ended up staying with us for several days.

It went really well, actually. All three of us are very fond of each other and the dynamics worked out very naturally. Highlights: At one point D. was disappointed that I hadn't talked about something with her, so he walked me into the bedroom where she was still getting up, bent me over the bed, spanked me, and then left me with her after letting her know where the whip was in case she needed it. Followed by her enthusiastically going down on me.

The bad news is that she has since left the country for a semester abroad, and won't be back until summer. We've been talking to her on skype and webcam, but we all miss each other a lot, especially since it wasn't until she was about to leave that we got together. I know that there isn't really much potential for a long-term thing here (she's still in school and we're probably moving next year), but I'm hoping that over the summer we will get to spend more time together.