Go. Be chill. You're making more of this in your head than exists from what you've described. You've gone out twice. You've had half a day of sexy time. She's likely going to introduce you as a friend since, well, that's what you are right now.
If you're looking for practical advice - show up about a half-hour after the party starts and leave when 75 percent of the guests have already gone out. Don't expect this to be a "date" between you two - force yourself to talk, however awkwardly, with some other folks in the room. Or just sit with a glass of wine and a mild smirk on your face - it'll make people wonder.
Most importantly? Have fun. It is a party afterall.