Well, I'm ashamed to admit this... I chickened out
I ended up taking photos of the 22 yr old, and we (she, her mom and I) picked a pose from the photos. She came back a couple days later, and I did work some from life. It seemed to look okay when she left, but as I continued to work on it from the photo, I realized that it just wasn't going to work. I'm not sure why it's not working. It could be that I toned the canvas a dark blue/gray. I can't seem to overcome a very cold feeling to the portrait though the photo and reality was warm enough.. I'll need to begin again. She was only here for a week and won't be back in town again till Christmas.
I feel I need a little practice painting friends or models from life before starting with paying clients. Or maybe I'll offer to do some for a drastically reduced rate so that I can gain experience.