I can see where she's coming from though. Like she said, she had hardships, but I'm sure she doesn't want a girl with no "rich people" experience to marry her son and runaway after all the stress gets to her. Or make her son be ostracized by the rest of the family. British nobility is more snobbish than Japanese nobility
The way she did it made it clear she wanted someone from a status family and lineage. She purposely intimidated. There's a way to say, "You make my son happy, so let's see what we can do to get you ready to face your duties as his missus." Instead, she gave her no chance and set her up to feel crushed and overwhelmed.
And the truth is, as a mother, I'd want my son to be with the person who gives him joy. Up to now, he's had no happy relationship. Now, he laughs and feels right with someone. Nobility can suck ass. There are plenty of divorces and cheaters and wife beaters among the nobility--look at the British Royal Family. All the kids got divorced, and one messily--Anne, Andrew, Charles. They all screwed up their marriages. Marrying within a circle is no guarantee. And does it look like the kids want to be caught up in nobility/status limitations? They look like they want to live normal lives.
Parents imposing their standards of a mate for social-status reasons is one of the worst. It puts money and position above self-actualization and love. Of course, we know it's a story and needs conflict, so the mother has to be a conflict-source. I get that. But she didn't even try to find out WHY her son chose such a "plain" and unaccomplished gal. That should have been job one: why. Because if his reasons are good and he clearly feels happy with this person, then the mother's job is to see how she can support them to make it work.
After all, the grandmother--a Brit--married a Japanese man, which was surely breaking taboo for her generation. And they were happy. :)
Well, that mother sure is one major snob bitch. Geez.