Hmm, I think you're right. When she says feminism depends on "a concept of sex class" and "the language" to discuss "sex oppression," that's what it may boil down to — desiring to preserve cis women's victimhood status. She seems to be saying that, if trans women are women, then the meaning of "women" dissolves, so no one can talk about women's oppression anymore, hence there can be no feminism. Thus, trans women's existence as women (disintegrating any usable concept of "woman," in her mind) destroys feminism and so revictimizes all cis women (as there is still a fact of who's female, as she sees it, even if no one agrees on it). Yes, I think that's her point. Something about preserving the unchanging essence of cis women's victimization, viewed entirely apart from trans women's experiences.