Ben convinces Darlene to get a refund for the airline tickets because they need the money. Tickets can only be refunded to the original form of payment, so the refund would go to Molly's credit card, not Ben and Darlene.
Molly Tilden's mother (or possibly stepmother, as Molly's father was described as a single dad in the original Roseanne) asks Darlene to return a casserole dish engraved "Tilden", saying it was her grandmother's. Molly got her last name from her father. Her maternal ancestors would have had different last names.