I keep feeling that the next panel of this comic, if there was one, would feature Tai replying: "I do too have a cock; right here (taps wherever she feels relevant), where it counts."
Anyway, I think the point, if there is one*, is that Tai sees Marten's female friends as more stable people than hers tend to be. Which is a rather frightening idea, but perfectly in line with the condition of most college students, all of whom are, of course, insane.
(At least I know I was, and lets not even talk about the people I went to school with.)
*Still hoping she's joking.