What Should I Do If I Dress up as the Male Protagonist's Vicious Sister?

What should I do if I am a vicious female supporting character in a book and know that I will die in the future due to the male protagonist's plan? Of course, while the male protagonist is still young, hug his thigh tightly. It's a pity that the vicious female supporting character is used to lying to the male protagonist, and the male protagonist's thigh is not so huggable. If it doesn't work, then find another one.