Welch, 63, will star as Chrissy, who tries to swindle Reynolds' character, Sam, and his friends out of their retirement plans, Zap2it.com reported Friday.
"It was really just terrific to see Burt again," said Welch, who co-starred with Reynolds in 1969's "100 Rifles" and 1972's "Fuzz."
"He looks great and is still as charming as ever," she said, "a wonderful guy."
In the film, Sam is a Vietnam veteran who gets caught up in Mafia mayhem when an East Coast wise guy, played by Michael Paloma, ends up in the witness protection program in the same Arizona mobile home park.
Robert Loggia and Charles Durning also star in the film as Sam's friends.
"Forget About It" is currently in production in Mesa, Ariz., and Hoboken, N.J., is set for a Thanksgiving release.