After the loss of his parents, Bruce Wayne didn't have many to turn to. One who happily gave him an ear to speak to was Dr. Leslie Thompkins. An old friend of Thomas Wayne, she felt it was her duty to make sure that Bruce made it through the ordeal.
Bruce trusts her so much that she openly knows he is Batman, and knows most of the Batfamily, and if Bruce is in serious need of a doctor or medical opinion, she's usually the first person he goes to.
Leslie is kind, and believes in helping people, which is what makes her a pacifist. That being said, she's not afraid to stand up to anyone, including Bruce. She even severed ties with him once after the death of Stephanie Brown. However, she came back later and reconciled, she just can't leave the kid alone.