Shuffle and cut the deck in front of your spectator.
Spread the cards out and have her select one.
Take the card back and your misdirection skills will now come in handy.
In your hand, break the cards in half and ask if that looks about even. At the same time, use your pinky to subtly lift the top card a bit.
Bring the chosen card behind the deck and pretend to place it into the middle. You are actually placing it underneath the top card.
Quickly close the deck and square it up. This creates the illusion that the card went right into the middle of the deck. Have her snap her fingers.
Double-lift the top two cards to show how hers jumped from the middle to the top.
Turn them back, face down, on top of the deck. Take the top card (which she thinks is hers) and place it into the middle.
Have her snap her fingers and turn over the top card to reveal hers has again jumped to the top!