Its not totally implied but the dialogue with Kiyoko where she stops herself when she says ''something changed in her when, oh never mind what matters is we are together now"
To me this was more of an acknowledgment of Kinu losing her childhood. Eventually as time went on she realized she couldn't be the spoiled kit who got fruits and pets from the Champ anymore so she stepped up and matured. Assuming this dialogue doesn't change based on whether or not you get hime or shoujo kinu of course. If its the same line regardless then it could also be seen as Kiyoko talking about when shoujo kinu finally decided to fully rebel against her mothers teachings.
the fact she is very robotic with you whereas with Kiyoko and the other kitsunes she is very friendly towards them
She's not robotic she's just mindful of her station and the Champ's. She's aware that acting like a spoiled child is unbecoming of her position. Its kind of a weeby and extreme depiction of Japanese culture but they place extreme importance on respecting their elders. It may not seem like it but Kinu is being friendly with the Champ even if her responses feel a bit cold due to her formal tone. If its hime Kinu we're talking about I'd argue that her friendliness towards the other kitsune is a measured reaction meant to maintain outward appearances.
The dialogue you have with her when you speak to her to me feels very resentful given you taught her how to hide emotions and the champion always seems to notice it.
I Disagree. To me its the perfect depiction of someone who is trying to do things alone so as not to worry or burden the people close to them that they care about. It doesn't help that due to her proclivity for learning things quickly she puts a lot of stress on herself to be able to do things correctly. Furthermore Kinu is aware of the Champ's mission to stop a demon invasion, it wouldn't be a big assumption to say that Kinu didn't want to put any additional stress on her dad by talking about things that may be distracting from your bigger mission at hand. We see this same logic with how Kiyoko responds to the Champ when they bring up Kinu's engagement. Kiyoko tells the Champ to their face that she didn't want the Champ to worry over it and that's why she didn't say anything. Hime Kinu probably follows the same thought process.
Also its kinda implied with who she marries in both, with kitsune hume she marries a person who dislikes you, with inari shoujo she marries some who is like you. it is subtle for some things but obvious in others.
I have to agree with what Ace said in their post. I think that Kinu's marriage candidates is more of a reflection of her relationship with Kiyoko and her acceptance of her position as a future den mother rather than how she feels about the Champ. Don't interpret this as an insult or anything but to me its a bit narcissistic to assume that your child would marry someone just because they did or didn't like you.
My final point is this; If Kinu really was resentful towards the Champ why would she allow the Champ to pet her? Its not like she can't refuse, we see her do this when the Champ tries to touch her tails/face depending on the version. We know that kitsune don't treat headpats and whatnot lightly due to their physiology and they are very careful with who they allow to pet or touch them due to it. No matter how friendly you're pretending to be towards someone I find it highly unlikely a kitsune would allow someone they secretly resented to touch them in such an intimate fashion. Thoughts?