
The way they said it before ursch growing obsession with MC it's probably something he inherited from her mom. Cuz the dad seems sorta normal. She must have done this indirectly to confirm her son's marriage. I think she has ties with the royal family or she would not have know about the King's offer

They are talking about Ursch's speach about how the merchants are constantly compared to dragons (in a pejorative way) due to their love for money. And he said that, like dragons, they(?) also tend to choose a treasure, be it a person or an item, and cherish it for life. For Ursch, it's the MC. He didn't specify whether this applies to all merchants or only for his family.

Tbh I wouldn't go so far as to call it obsessive, but the author / translating team did use that word to describe it:
http://www.mangago.zone/read-manga/the_villainess_want_to_marry_a_commoner/mpn/mpn_chapter-1958467/pg-14/
And he does mention that she doesn't have a choice - he will never let her go:
http://www.mangago.zone/read-manga/the_villainess_want_to_marry_a_commoner/mpn/mpn_chapter-1958467/pg-16/
http://www.mangago.zone/read-manga/the_villainess_want_to_marry_a_commoner/mpn/mpn_chapter-2031789/pg-8/
And that she is "his possession", though that probably has to do with some merchant specific skill:
http://www.mangago.zone/read-manga/the_villainess_want_to_marry_a_commoner/mpn/mpn_chapter-2031789/pg-8/
Anyway, I'm just pointing out where @Xylemthegreat was coming from. ╮( ̄▽ ̄)╭ I don't really feel like Ursch is obsessed with Isabella. Or at least not yet.
Who was that "Madam" ordering the merchants to let everyone know about Isabella's engagement? Ursch's mother? Isabella's mother? One of Isabella's sisters? Or a new character that we have yet to meet?
Obviously is someone who will profit somehow of the alliance between the Rottenstein and Schneiver families being made official. But if it's a new character, there are way too many possibilities. As Isabella said, her family is ridiculous gifted and accumulated WAY too much political power through the marriages of her siblings.
And maybe her marriage to Ursch won't necessary balance things out. They seem to be a growing merchant company and bound to become even bigger with Ursch in command and the Rottenstein's support. So now not only they have political power (sisters' engaged to neighboring prince and borderlands count), military power (brothers being engaged to the daughters of the heads of the mage division and imperial knights) but also monetary power (Schneiver Company). They could possibly dethrone the royal family if they wanted to!
So I think that the lady in the shadows most likely is someone from the Schneiver Company. She could also be someone aiming to destroy the Rottenstein's by making them a threat to the royal family. Maybe even a royal who is already feeling threatened and either wants to build them up to bring them down latter OR truly believes that by marring one of their daughters to a commoner they will lose face in high society.
What do you think?