My advice is to throw in some NPC allies. Make them friends, family or associates of hers (the PC), not just henchmen. Play up their relationship, maybe even make one of the NPCs the de facto leader. Shortly after the adventure begins, however, you can take out the leader in some dramatic way. Then, perhaps, have the other NPCs look to the PC for leadership from that point on.
You can, throughout the adventure get rid of these NPCs whenever you like, of course, perhaps leaving the PC as the only survivor (giving her good reason for joining your official party). Having these NPCs be more than just hired help, however, will give their deaths (and their lives) more meaning to the PC.