This psycological thing you talk about is what makes pro go interesting for me. I have written about this before. I don't expect my posts to be remembered (

) but when I try to forecast the result in a game, I do it thinking in the mental attitude of the players. That's where Iyama shines, in my opinion.
The raw ability of top pros is more or less the same. Or used to be. In these early times of AI, the one who manages to get more from it has an advantage. But in the end, the knowledge will be there, games can be studied by everybody, and differences will be small. It is better to be a tiny little bit stronger than your opponent, rather than weaker (is my English right here?) of course, but in the long term, results don't reflect only that. Back to Iyama, is he really so stronger to everybody else? Stronger enough to hold all 7 titles at the same time? I doubt it. He lost games too. But his mind must be strong enough to hold the pressure when he needed to, and keep focused for many hours.
Now, back to Rina and Sumire. If Rina has been following Sumire since Sumire was 5, it means since Rina became a pro, or was about to it. Although Rina lives in Tokyo, and Sumire is from Osaka, it is a small world. Perhaps many pros knew that Nakamura Shinya had a daughter who looked pretty good. Rina's father, Fujisawa Kazunari is a bit older than him, but perhaps they know each other. Maybe this is just gossip, but a new promising new dan, thinking about a 5 yo girl... that was news to me.
I don't know what's Sumire's secret (

), but... her father is a 9-dan, probably one of too many, and her mother is a go teacher too. They know about the go world, and have probably taken a lot of care in protecting her, aside from teaching her. I can think of Rafa Nadal's case, how his family and environment have a lot to do with his mental strength. Seems to me that Sumire is not someone who would rate herself with a 10, but rather would think about how to improve.
I don't know about any match between pros coming from go playing families. Cho U is married to Kobayashi Izumi, and fought Hane Naoki a lot. This is the closest I can think about.
As for the result, ability-wise, I expect a 2-0 for Rina. I am sure everybody, including the players, expect the same. That means that the pressure will be 100% one-sided. The surname Fujisawa is a lot heavier than Nakamura.