I literally created an account on this site just to comment on this story. Because I liked it that much.
I like seeing how other Umas react to how strange Shirogane is, an Uma who behaves more like a human in many ways.
Even though Shirogane is a high-functioning sociopath in all her lifes, thanks to the good upbringing her first parents gave her and clearly instilled in her a firm value system based on reasoning and logic, despite being a sociopath, she remains decidedly human, both mentally and spiritually.
This is noticeable in how she never gestures with her ears or tail; she is much more severe and taciturn than others, and above all, her lack of passion for running must produce an uncanny valley effect in other Umas. Even other stoic Umas like Mihono Bourbon regularly gesture with their ears and tails and still maintain their passion for running.
After all, Umas were literally born to run. Even though they can develop other passions and interests, running is always a fundamental part of their personality. Shirogane, an Uma who clearly only has a financial interest in running, must be as baffling to them as a human who never blinks and doesn't enjoy eating or drinking water is to us.
While for practically all Uma their first professional race is a "canon event" that marks a before and after in their lives, for Shirogane it's more like: "Oh yeah, I went to the dentist yesterday, nothing interesting happened." It's no surprise that Shirogane's friends are so surprised and even hurt by not being invited; it's as if she's telling them she doesn't really consider them friends.
These differences seem only going to become more pronounced as time goes on. Some of her friends, like King Halo or Grass Wonder, will probably start to resent how good Shirogane is at something she clearly doesn't even enjoy that much, and Shirogane will start to feel strange about how obsessed the other Umas are with running, as if they have no other goals or dreams in life.