Miho's Past
From what Miho says of her past, one would get the impression that she neither liked nor was good at tankery, and was unhappy and unpopular at her previous school until the incident that resulted in her leaving tankery and coming to Oarai. But is this necessarily true?
First, let's consider Miho's claim that she never liked tankery. To begin with, all the information we have about Miho's feelings are what she tells us, the viewer. This information is likely colored by her perception of back then; she left her old school on a bad note, with the incident being enough to make her want to leave tankery behind forever. As such, it's likely that Miho essentially judged the entire story by its ending, and concluded that her time at her old school was not good, nor was her time in tankery until she came to Oarai. Perhaps she is happier at Oarai, but it doesn't necessarily follow that she was never happy at her old school.
But there is a flashback series- the Little Army manga- that sheds light on how Miho had happy memories of tankery. To briefly summarize it, Miho found tankery a lonely and not very fulfilling pursuit until she made friends through it. She idolized her sister and sought to emulate her, but learned of the difficult choices her sister must make. It then became clear to her that in order to continue in tankery, she must find her own path.
The entire point of the Little Army manga is that for Miho, the problem isn't with tankery; it's with the family style that forces Miho to go against her own moral code and put victory above everything else. This is why Miho's sister Maho is willing to be the Nishizumi heiress to allow Miho to go her own way, and why Emi is insistent that Miho not give up on tankery in the final chapter. What happened in the intervening years is less clear, but it's evident that Miho now has a goal to which she can dedicate herself.
Of course, when Miho finds herself in a situation in which the only way to save her friends is to jeopardize her team's chances of victory, she learns that her mother will not tolerate such decisions. It's indicated that Miho believed that long as she was in tankery, she would have felt such pressure again in the future. And believing that there was no way to do tankery while disregarding her mother's commands, Miho likely began to see it as hopeless, and, in her mind, gradually thought less about the pleasant aspects so that she could leave it behind and move on with her life.
Of course, that didn't end up happening, and Miho got involved with tankery at Oarai. Initially, she was apprehensive about the pressure, an understandable reaction to a student council that seemed almost obsessed with winning the tournament (not without good reason, as Miho later learned), and was reluctant to take on the responsibility of being a team commander. However, over time, she began to enjoy it, and take part in it more willingly when she saw that she could help her friends. As such, by the time she realized that she had to win the tournament to save the school, she had progressed to the point at which she stopped seeing it as undue pressure to win, and more of an opportunity to keep her friends and school community together, something she wanted to do. When Miho's fighting for something, tankery becomes more pleasant; to sum it all up, Miho went from wanting to quit tankery due to feeling lonely, to doing it with her friends, to trying to find her own way of tankery, to believing that was impossible and wanting to run away with it, to rejoining because of her new friends, to fighting to do tankery her own way for her school and her friends.
As for her friends, Episode 10, when Miho sees one of the people she saved. Koume calls her "Miho-san", a polite yet friendly address similar to what Hana calls Miho. Now compare Erika's mocking reference to Miho's former position, as someone who only knew Miho as a possible rival for her position. This would indicate that some of Miho's teammates viewed her as a friend as well as a superior.
As for the rest of Miho's schoolmates, apart from Miho's sister and the aforementioned Koume, the only person who seems to have a problem with Miho is Erika, who's a fairly unpleasant individual. It's difficult to tell how indicative Erika is of the rest of them, but the fact that Erika succeeded Miho as vice-captain indicates that Erika is likely one of the more driven and ambitious individuals in the school. She sees Miho's decision as essentially betraying her school, and will not tolerate those who do not give their all in pursuit of victory. It's hard to tell whether the majority of the students from Miho's old school are like Koume or like Erika, but this could indicate that they're not entirely bad, and that Miho left friends behind.
In the end, I don't see this as a internal inconsistency or even proof that Miho is lying. Her experiences color her perspective on tankery and her old school. Perhaps there will come a time when she speaks fondly about her old memories, sees her time at her old school as a step in her development as a tanker, and reconnects with her old friends.
