The first picture shows her with a "Tab" pulled up to reveal the sentiment. A small purple brad allows the sentiment to remain hidden until the pink arrow is pulled up. You will have to play around with measurements to "hide" the sentiment underneath the main image.
Here you see the pink arrow "tab" directing the recipient to pull out the hidden message. This is how the card looks when it comes out of the envelope.
Again, once the pink arrow is pulled up, the message is revealed.
This is inside the card. This image is from Inky Antics. ("Hi Chickie" as well.)