My Best Friend is the Villain

Chi Tingxia transmigrated into the body of the villainous young lady's lackey in a novel, but she discovered that having the young lady as a cash cow was incredibly lucrative. To change her and the young lady's fate, she vowed to be loyal to the young lady and make money! She slapped the villains and silenced everyone with her words. Why did the young lady unconditionally support her, and why did the young lady's brother secretly love her?