Wow, it’s actually really refreshing that Nakajima isn’t the first woman that Mihoko had semi-romantic feelings for. So often it’s the pursuer has experience and the person being pursued is completely oblivious to the advances of the other, and I think it’s good for both of them if she already has her attraction to women figured out, more or less.
It’s also interesting that there’s a real possibility of her being a lesbian, it’s pretty common in real life for women to only realize their sexuality later in life, even after having children and marrying a man, but those kinds of people don’t usually get represented in media.