At the end of the episode, Jonathan gives Jennifer a heart-shaped red stoned ring. She's already wearing a ring that is narrow and shiny (tiny diamonds?). In the close-up of Stefanie's hand, the ring she is already wearing changes to a wider gold band.
As Jennifer, Stefanie keeps her fingernails relatively short. When Jennifer is talking on the telephone, there's a close-up of her right hand. The fingernails are much longer.
The chocolate shop sends a Valentine greeting in a card with yellow flowers.
When they're just setting up the plot, the bad guys suspect their accomplice of stealing what's in the heart. Since it's unbroken, that wouldn't be possible.