I've actually known some stereotypical sorority-ish girls who use "sis" / "sister" in a very parallel way (shallow, narcissistic, petty, immoral). Doesn't someh

I've actually known some stereotypical sorority-ish girls who use "sis" / "sister" in a very parallel way (shallow, narcissistic, petty, immoral). Doesn't somehow invalidate all use of the word. (And obviously not all sororities are like that, hence "stereotypical". Nor are all fraternities.)