The main thing is to be real. If she actually is a close friend, she will be able to tell if you are putting on fake attitudes around her, and that will make it ever so much more awkward. Be yourself, give her brochos for her own success, ask your chosson if he has any friends for her. Obviously don’t shove it down her throat, but include her as you would any of your friends. And the most important thing is – DONT BE PATRONIZING.
And ignore everything I just wrote, because nobody could possibly advise you without knowing you, the girl, and your relationship. This is one of those Every Case Different situations.