All of the “life flashes before your eyes” scenes were recreations of moments from their life. She apparently had no idea it was a proposal until the final three seconds of the video, while they sat in a theater full of family and friends. It turns out he rented out a theater and invited their friends and family. This trailer played in the midst of some other ones so as not to start out conspicuously.
She did say yes and they do have a child now!