If I remember LN correctly there was a side story where Emilia was reminiscing about some things with Tobias before and after he broke the engagement. Basically she's feeling like he's comparing her to MC, which he wasn't, and not measuring up to MC. Made up story about necklace being missing to try to make MC look bad to Tobias. Feels MC dyed her hair (washed dye out actually,) and stuff to get attention among other things. As a result Tobias is working a lot partially to earn a living and partially due to mess he made over breaking engagement. Emilia not helping to avoid being compared to MC, and her misunderstanding Tobias being much more well off than actually is. Sure he's part of the family company, but most of the money company makes goes back to company or senior family members. His mother thought could get a line in with nobility which is why agreed to Tobias marrying Emilia rather than MC, but doesn't realize that Emilia wasn't acknowledged by much less ever met her father. Only knowledge about nobility is what's seen, the necklace, and stories about her father from her mother.