I doubt she's second guessing; she's put off moving out because its big step for her to take and its scary, but now she's ready.
Part of DBing is to do the unexpected. She expects you to try to delay her move. Don't do that (it's pursuing). Help her toward her goal. I bought my wife a bunch of boxes and packing material when she was moving out. It was a kind-and-gentle little push out the door. Show her that you'll be just fine (or maybe better) after she moves out.
