There are no good responses unless they are ****y and funny responses.
So when are you and your girlfriend moving in together?
Finally coming out of the closet huh?
I've seen your future and it's cats, cats, and more cats.
(warning, you will be labeled a jerk for this. Probably best not to do that at all).
The creeper move? A private message asking her out for coffee and ignoring her post all together. It's the cry of a empty vag bro. Creep that azz bro! (said in obnoxious bro voice).
Of course like in the movie Wargames. "The best move is not to play". No response is a better response.