One possible motive could be power play. The teen girl might be in a position where she feels powerless in other aspects of her life, so she exerts power over the old man in this extreme way. Another could be a form of rebellion against social norms. By making the old man crossdress, she is challenging the traditional gender roles that society has set.
Perhaps the girl has some psychological issues. Maybe she has been through some traumatic experiences related to the old man or men in general, and this is her way of getting revenge or expressing her anger. Or it could be for shock value. In a world where getting attention is important, she might think that such an extreme act will make people notice her and her ideas about breaking gender boundaries.
Look to Chapter 195 for the clearest answer. It begins with Jiang Yan was fully equipped and followed at the end of the team., keeps building through He was wearing a sports suit borrowed from He Yun, his face smeared with..., and lands on The audience and fans would definitely think she was.
A practical answer is Chapter 200, because it turns the idea into a concrete scene. The chapter opens with Shang dismissed the thought of turning around and walking away., adds pressure through She scoffed in front of the door at this man's hypocrisy, then left., and ends on Are you doing this on.
If you want the clearest chapter reference, go to Chapter 184. Early on, Jiang Li can finish the competition alone???; later, the chapter leans on Then isn't the championship undoubtedly hers?.
A practical answer is Chapter 199, because it turns the idea into a concrete scene. The chapter opens with Damn, the production team is actually being so generous this time, giving..., adds pressure through Daniu finally showed up again, I've missed you so much!], and ends on You knew all along?".
Chapter 286, "Bloody Chainsaw", is the clearest early answer because it turns Bloody Chainsaw's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Killing the Chainsaw Zombie brought Wang Tao an Advanced Special... and follows through with He had gotten five bottles previously and, after using them....
A practical answer is Chapter 199, because it turns the idea into a concrete scene. The chapter opens with Damn, the production team is actually being so generous this time, giving..., adds pressure through Daniu finally showed up again, I've missed you so much!], and ends on You knew all along?".
A practical answer is Chapter 207, because it turns the idea into a concrete scene. The chapter opens with After finishing, Sister-in-law Lan quickly took out the Good Evaluation..., adds pressure through I didn't say I'd pay you for your work, did I?, and ends on She had taken care of them for a.
If you want the clearest chapter reference, go to Chapter 189. Early on, Seeing his painstakingly planted roses trashed like this, even as a fan of...; later, the chapter leans on Wenwen, I beg you, please take good care of my land!" "LOL, since when did....
If you want the clearest chapter reference, go to Chapter 194. Early on, Director Sun, this isn't another one of your production team's wicked...; later, the chapter leans on Making me the guarded King all the time?" Director Sun, whose little....
The best chapter pointer here is Chapter 197, "Dear Brother". It opens with Seeing that no one cared about what she said, Su Yinwan immediately felt... and closes on Wen Jiaojiao, aren't you underestimating me?.