Trial shoot. Deffo. Finding someone willing to work TFCD or at a reduced rate with a view to further fully-paid bookings is ideal. They then know they have to perform well in order to gain repeat booking from you.
Pick one with a broad range of images where she looks sufficiently different in each.
What you're after is a blank canvas to imprint you own vision upon, not just repeat her earlier styles.
Book a two-hour test shoot (that doesn't mean two hours of shooting BTW - allow 30 minutes make-up and prep time as well as a tea-break after 45 minutes or so) and shoot a quick series of shots with at least one costume-change. That'll give you a heads-up as to her personality and suitability for future projects.