Bai Meiyue was filled with satisfaction when she saw her brother awaken.
Yup, she deliberately ran downstairs because she knew that Bai Zhan would follow her. In her last life, she also awakened when she felt cornered and scared; thus, Bai Meiyue tried to use the same tactics at her brother.
She knew that, as her eldest brother, Bai Zhan was much more protective of his siblings than she was of her son when she was pregnant with him in her last life. And yet she was still able to awaken, so compared to her, Bai Zhan's chances were even higher.
As for why he awakened a different set of powers, Bai Meiyue did not care about it. Instead, she was quite glad that her brother was able to awaken as a defensive-type supernatural being.