To everyone confused:
Shuli wants to prove that the marriage was never consummated (aka she neve had sex with her husband) so she can annul her marriage and let Jeremy be head of the house, which for some reason means he gets released (idk why lol).
To prove she they didn't consummate the marriage, she'd need a witness but obviously her husband is dead and can't testify. However, she found a letter where it is hinted that he said that they didn't or won't. Since the letter is addressed to his previous wife's family, I assume it says something along the lines of "I'll always love my old wife, I won't betray her and consummate this new marriage" or something. However, she apparently needs a second witness along with the letter, so she wants the intended recipient of the letter (previous wife's brother) to be the witness. I maybe think the letter references a discussion her husband had with the brother about not conaummating the marriage or something? Idk. Anyway, the brother refused to see her, so she's asking this bitch to help I guess somehow.