Warslayer is basically Galaxy Quest meets Xena, with the star of a syndicated fantasy-adventure series being magically transported to a fantasy kingdom where she's expected to be "Vixen the Slayer" for real.
It also sounds like the TV movie The Adventures of Captain Zoom in Outer Space from 1995 (predating Galaxy Quest by 4 years), where it was the star of a 1950s live-TV Captain Video type of sci-fi show who got transported to a distant planet by someone who mistook him for a real space hero.

