Bruce Wayne's parents died when they were mugged in an alley. The criminals shot them, leaving Bruce orphaned and shaping his path to become Batman. This event had a profound impact on his life and motivations.
He might develop a greater sense of humility. Without the Batman persona to fall back on, he has to face his own limitations as a person. For example, he may struggle to get people to listen to his ideas for change when he doesn't have the intimidation factor of Batman.
Often, she is depicted as being just as intelligent as the male Bruce Wayne. For example, she has a sharp mind for detective work and strategy. She might be able to quickly analyze crime scenes and figure out the motives of the villains.
At first, it could be a bit rocky. Bruce is used to his own way of doing things and Buffy has her own independent streak. But they would gradually learn to respect each other. Bruce might be impressed by Buffy's combat skills and her ability to handle the supernatural. Buffy, on the other hand, could learn a lot from Bruce's strategic thinking.