Yeah, I mean CookieMonster covered most of it, but I disagree with your interpretation. Asuka wants to be close friends with Tomoko, and Tomoko is usually the one being 'crass' around Asuka. Asuka just doesn't want Tomoko to be reserved around her. Even if it were the case that Asuka was the one being lewd/crass, it's completely normal for friends to talk about crass topics with each other. Asuka has never done anything or acted so unhinged as Tomoko's other classmates have.