I like your assessment, and I wonder if Kyou is maybe upset because she's seeing some of her (very noble, to be clear) self-sacrificing behavior is actually harmful in its on way to how her daughter understands family and relationships. IMHO Minori could be on the path to having a real toxic co-dependant nature, and Kyou sees that and doesn't want that to be the lesson she passes on.
I think I largely agree.
My view is that Kyou sees Minori at risk of becoming like herself--someone who has to 'give up on their dreams' to address the immediate concerns of the present and of those around them.
Kyou did that for Minori. As you said, it was necessary for her--but it extends back before that, even, when Kyou had to leave college/break up with Takaharu. We still don't have the explicit reason as to why, but it seems to have had something to do with "family circumstances"--meaning Kyou gave up her own pursuits to go back home, for whatever reason, and start being a working adult immediately.
And it wasn't all bad--it lead eventually to Minori coming into existence, which is inarguably a net positive for Kyou.
But Kyou went on to sacrifice herself for Minori's sake all through the daughter's life, and she's
still doing that, rejecting potential happiness with Takaharu just to ensure Minori's needs are met.
And now, she's seeing the result of all of that. It was all necessary, and reasonable, and I'd argue justified--but it's left Minori feeling like she has to shoulder half the burder with her mother. Something Kyou has never wanted, but probably never gave significant thought to being a possibility (or, until recently, hasn't had the
time to reflect on it).
Which is how Takaharu will factor in. Because he represents a place of stability wherein both Minori
and Kyou can finally rest and attend to needs higher up Maslow's Pyramid, as it were. If Minori can be certain that Kyou "doesn't need her", she can move forward with pursuing her own dreams without feeling fearful or conflicted.
And it's a nice little bit of symbolism with how many parents are in the real world. A lot of them (hopefully) want their children to succeed where they might have failed--to have opportunities never afforded to themselves. So they'll work themselves to the bone to see their children want for nothing, and have that support base to pursue their dreams.
Kyou has done that for Minori, after (seemingly) having no one do it for her. It wasn't
quite enough (and that's not an indictment on Kyou), but now she has someone who is able, and even willing, to help her shoulder that weight of responsibility.
And with Takaharu doing so, Minori can finally breathe, knowing her mother is being cared for, and she can start looking ahead to her own life.