As Twilight Horses – Demon Rider (which also contains Transitions by Jane Ayres)
I think the Salma story first appeared in the Demon Rider volume, before appearing on its own. The synopses are certainly remarkably similar!
Salma watches a stunt horse being readied for a film, with a mysterious, ghostly rider. The rider isn’t Ryan, on whom Salma has a secret crush, and whose horse Red is. Who is riding the horse?