To all the people saying she's a coward...she's already made a bunch of moves. In fact, almost everything that's happened between them has been initiated by her.
Why should she have to put all the effort in?
He's a coward who needs to get it together and make a move, any move. She gave him not one, but two perfect opportunities to ask her over. Too much of a coward to ask her over directly, and too much of a coward to use her little brother as an excuse to have them both over.
"Not ready" my ass.