Eleven student screenwriters shared $9,000 in prize money Tuesday afternoon when the UCLA Extension Writers Program presented the second annual Diane Thomas Screenwriting Awards. First place winner of $5,000 was Susan Vaughn of Beverly Hills, a free-lance journalist whose script titled "A Cheerleader's Story" is based on the murder of a cheerleader in Marin County a few years ago. The second prize of $3,000 went to Alexandra Sokoloff of Los Angeles for "The Mindworm." Christine Macgenn of Suisan, Calif., got third place and $1,000 for her script titled "Ulysses." Last year's first-place winner, Randi Allison Mahem, sold her screenplay, "A 22-Cent Romance," to Orion Pictures for $350,000 and Dennis Quaid has committed to co-produce and star in it. The awards honor Thomas, who studied with the UCLA Extension Writers program in late 1970s and wrote the script for the 1984 film "Romancing the Stone." She was later killed in a car accident.