Priestess' life was saved by Goblin Slayer when they first met. Ever since, she has been his loyal companion and friend. No matter the objections she may raise when it comes to Goblin Slayer's methods and attitude, she will be the first to come to his aid.
On the other hand, Priestess takes the time to lecture him when she thinks he is going too far; and even when he shows his annoyance, she isn't the type to easily back down.
Priestess looks up to Sword Maiden because of how powerful and beautiful she is.