Around CH 10 Mrs Brennan who was the palace head maid and Erin;s nemesis hears about Erin's cafe plans, and it's implied contacts a merchant friend to lock her out of buying coffee (the friend has a monopoly). Erin takes the garbage beans she was sold and the receipt and makes them a gift to the emperor with the threat that he will lose his monopoly. After he caves, she extorts damages out of him.

THAT'S HOW YOU RUN A BUSINESS!!!
THAT;S HOW YOU NEGOTIATE !!!
I wasn't thinking about it at the time, but anyone who has ever had to deal with business problems with "connected" (shipping, garbage, alcohol supplier, linen laundry) suppliers can recognize this.

Erin : The Duchess MC and a marquess in her own right. Her family was on the verge bankruptcy prior to the start of the story. Her father was the last in line to inherit the title. She married the Duke to save her family

Raymond : The Duke aka Ex Husband. He's forced into marrying Erin by the emperor. Unable to do anything about it he vents his anger on her. He has a mistress while never consummating the marriage with Erin.

Erin's Father: Originally a poor knight, became a knight commander after inheriting the marquis title. In order to get Erin out of the marriage he fought bravely to gain military honors, unfortunately died in the process

Erin's Mother: Daughter of an immigrant baker, she is where Erin gets her cooking ability from. The death of her husband drove her to death.

Mrs. Brennan/Blennon??: Head maid of the palace active enemy of Erin during her marriage. Fired by Erin on the day of her divorce. Step mother of Serena has all her hopes riding on Serena's ascension

Calix: Raymond's adopted brother, possible ML doesn't like Serena or Raymond

Einz: Erin's Childhood friend. The correspondent in the accusation of her affair, both he and Erin were covering up the fact he had been infected with devils poison

Melly: Erin's loyal maid and first employee of her coffee shop

Serena: The mistress

Setup:
Erin's family is fallen marquis, they are left with nothing but the title, a mortgaged mansion and a mountain of debt.

As the family is to be sold into s*avery, Erin is informed that the emperor would like her to marry his grandson the Duke. This is done to put a leash on the duke and prevent him from trying to take the throne.

After 9 years Erin is framed for having an affair. The Duke moves behind the emperor's back and gets a divorce. Erin is more than happy to to get out.

As a note she holds the seal of the empress entrusted to her by the emperor not the duke, so she uses it to fire Mrs. Brennan who had been scheming against her. Mrs Brennan vows revenge in a way that would do a Xanxia character proud

She does NOT wind up back with her cheating ex! Feel free to enjoy the story, safe in the knowledge he is well and truly kicked to the curb.