Joyce Summers

The premise of the series is that Buffy is the latest Slayer, a young woman endowed by mystical forces with superhuman powers to fight and defeat vampires, demons, and other evil forces in the fictional town of Sunnydale. Like every Slayer before her, she was chosen and informed of her destiny when she was 15 years old. Her mother is unaware of her daughter's powers and responsibilities until Buffy is forced to tell her at the end of the second season of the television series. Although Joyce is shocked at this revelation, she recovers quickly and remains a source of stability for Buffy and Buffy's small circle of friends who assist her, dubbed the Scooby Gang. Eventually Joyce is able to take Buffy's dangerous demon-fighting in stride and even become proud and respectful of her daughter's abilities. Her natural death from an illness in the fifth season forces Buffy to face becoming an adult.

Question: does buffy's mom know she's a slayer
Answer: yes