Dee Horton was at her job as a hair stylist at a Cleveland salon waiting to watch the airing of the commercial last week, WJW-TV, Cleveland, reported.
"(He's) supposed to be some superhero in it," she said just before it aired.
"OK, there he is," she said as boyfriend David Jones came on the screen.
Surprise turned to shock and then to joy as she listened to what he was saying, WJW-TV reported.
"A lot of people say we're living on love, like it's a bad thing," David began in the commercial.
"How about you and I show the world what true love is all about?" David said, showing a ring and proposing.
Seconds later he entered the salon, where a joyful Dee accepted his proposal.
Horton, who is battling thyroid cancer, said David has been with her every step of the way.
Jones, who works in video production, said he chose the method of proposing because "it's something neither one of us would ever forget."