We have one girlfriend we'd like to invite, who used to work with us both. We're not as close as we once were, but she's indicated that she'd love to come to the wedding. She dates... a lot, since her marriage ended about a year ago. I'd like to address her invitation to "Jane Doe and Guest" since I have no idea who her current (or then) beau is/will be.
Would it be ok to include a handwritten note in the envelope saying something along the lines of "I'm not sure if you're seeing someone currently, but if not, feel free to bring Sally (her best friend and a mutual acquaintence of ours) or another friend!"
I definitely don't want her to have to attend alone, since we don't have many other people coming that she will know.