Garden of Madness wrote...
Ya know, I don't really like the change in personality of Minori. It's seems too sudden. And I'm starting to get the idea that there's something else going on with her aside from feeling guilty about liking Ryuuji. He asks her to go to the Christmas party with him and she says no. And you could argue that she was upset about breaking Taiga's star but that attitude started long before that.
Also, they haven't shown what she's like at home. I think that may be a factor in what's wrong with her.
BTW, Taiga was very cute sending her father Christmas presents despite his actions. And the orphans.
And Ami seems to have given up at this point. :?
Minori's personality has not changed. Did you forget when she burst out telling Ryuuji what a horrible, arrogant person she was earlier? Her eccentricity is merely a mask, a facade. Her mask is slowly but surely cracking into pieces and then falling apart.
You bring up the idea of being affected by her home life. I don't think it is likely that it would explain her current emotional state, at least not directly. I'm thinking this kind of scenario: Minori's father is abusive. This would help explain how she initially tried to get Taiga and her father together, and why she despises him for abandoning Taiga. It could then be reasoned that her workaholic nature is to stay away from home for as long as possible. Her eccentric mask would be her attempt at appearing to everyone that she's happy, though due to her unstable emotional home life, her version of "happy" dips into the "weird" region. Her self-proclaimed arrogance could either be from the belief that if she can survive living with her father then she can live through anything, or it could be her attempt at hiding something darker of her personality.
Ami giving up on Ryuuji actually makes a lot of sense, she's a person with very realistic expectations. That's probably from working in the "adult" world.