Maybe she was exposed to some ancient magic. It could be that she was in a place where there was a strong Parseltongue - related magic, and it somehow influenced her.
One reason could be that she has been studying so much about magic in general. She might have accidentally stumbled upon a spell or a piece of knowledge that unlocked this ability within her. Another possibility is that there is some sort of connection to her heritage that she wasn't aware of before. Perhaps she has some distant relation to a Parselmouth, and this has now manifested in her.
Chapter 319, "Sister Xiao Wan", is the clearest early answer because it turns Divine Sense's situation into a concrete plot event. The chapter turns that into something concrete by moving from Staring at the screen displaying "Sister Xiao Wan," Jiang Cheng...
Chapter 206, "Miss Su, Thank You So Much!", is the clearest early answer because it turns Uncle Lan's situation into a concrete plot event. It opens with Five minutes later, Xingxing led Ah Fu out of the room by the hand.
Chapter 596, "Then Blow Them All Up", is the clearest early answer because it turns Bai Lu's situation into a concrete plot event. The chapter turns that into something concrete by moving from Jiang Li shook his head without any expression.
Chapter 364, "This is the gift our master sends you for the first meeting", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event.
Chapter 174, "Such a Melodrama, Love Watching It", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. Early on, Does Young Master Jiang really care why I would come here?. By the end, She knows the camera is on her, how can she still..." Jiang Li....
Chapter 430, "I Quit", is the clearest early answer because it turns Zheng Xun's situation into a concrete plot event. The setup is Hey, do we join a team that's short on members, or do we form our..., but the pressure keeps building through I want to join Team A and follow Ji Yanbai..
Chapter 484, "Gu Yu Returns to the Country!", is the clearest early answer because it pushes Wagyu into a new phase or setting. A useful checkpoint is the way the scene starts with More raw meat aroma wafted over, and the boar that was on its last...
Chapter 177, "You Annoy Me Just By Being Here", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event. The chapter gives readers a real answer by opening on I'm actually the last?!" After the scores were announced, Wen...
Chapter 402, "The Survival Game Officially Begins!", is the clearest early answer because it turns Jiang Shixu's situation into a concrete plot event. The chapter turns that into something concrete by moving from What kind of face was it?
Chapter 294, "President, This Kid Says He Is Shiguang", is the clearest early answer because it turns Lu Xingchao's situation into a concrete plot event. The chapter turns that into something concrete by moving from Speak of the devil, and he shall appear. to You, have you come of age yet?.