[potchip]

This is borderline overanalysing but a person can have multiple, or even contradictory characteristics.

Kirino has this moe/siscon game fetish and its association with otakudom, but her interest is quite specific, non of the otaku-sage type who likes the culture and everything associated with it. It would be unfair to characterise her as a fan first and foremost because it is just one side of Kirino - just as valid as her hard-working model student side (her monologue in ep5 said just as much). She did tell Ayase that Ayase and eroge are just as important, and her refusal to abandon neither caused the rift. Kirino never 'choose' one over the other, Ayase choose to remove herself from the friendship and it is only because Ayase eventually partially accepted the other part which allowed reconciliation. Kirino did not compromise on her eroge part, nor would I think she would compromise on Ayase if the context is reversed, they are both important.

Edit: Some anime only viewers are overplaying Kirino's otaku interests. Can't fault them especially since ep9! Do remember however that her eroge obsession is built on the foundation of being a good student, a modelling career and other commitments. Without those she cannot have her hobby. Therefore it is a stretch to call those accomplishments 'fake' because they earned her the right to have this hobby.

Also another point of clarification:
Kirino is only really tsun to her brother. Her interaction with Kuroneko is not tsun because you'd otherwise describe Kuroneko also as a tsundere except both are simply bad at freely express themselves to people they care about. In comparision her reactions to Kyosuke which are extreme, follows no pattern and outright hostile. Remember the opposite of love is not hate, but in-difference. Kyosuke is special to Kirino, exactly what 'special' means are yet to be seen.

All this bagging her being selfish/immature are missing the boat IMO (it is only true in the context of Kyosuke). First i don't believe being dere means maturity or unselfish to begin with. Besides socialable is a skill and there are plenty of that (which made Kyosuke cringe) in the home visit episode. Another important revelation was during the Ayase episode, despite feeling horrible over the holidays she concentrated in the atheletic camp and her reasoning being "must do my best otherwise it is unfair for those people who were overlooked for the camp" which goes to show she does have emphthy even for your average joe guys and has the emotional maturity to stay focused despite personal demons. That to me shows more maturity than becoming an emotional wreck if that's your definition of a responsive character.

I believe Kirino used the eroge in ep9 as reference material. She was exploring the choices you can make and the consequences. She essentially decided to play as Kyosuke would do. The irony was despite her not seemingly recognising any progress with Ringo and the tsun level, she ended up on the Ringo route anyway. Implying Kyosuke is possibily on the Kirino route.