Qin Nianwan's alliance with Chen Huifang was not accidental; it was Qin Nianwan who took the initiative to approach her. When Qin Nianwan was reviewing the information Han Lu had provided her, she noticed Chen Huifang, a character with a gambling addiction and desperate need for money, who didn't care about familial ties – all traits that made her an easy target.
The day after learning that Chen Huifang had come to Shen City, Qin Nianwan had Han Lu find her. Han Lu barely needed to say anything to persuade Chen Huifang to agree to her plan, as she was indeed in need of money.
Moreover, Qin Nianwan could tell that she had her own plans and might even use this opportunity to demand a sum of money from Wen Han.