Recently i've been playing fallout nv as a female (i'm a 46 yr old guy) and right now i've got rex and cass as my companions and i've wiped out the van grafs in the silver rush and later the same day i also wiped out the crimson caravan, and while looking for a way to h&h tools i found the scorpians gang at the monte carlo suites and while fighting them cass says something like "Let's paint the place red!", cass really has some issues

I killed everyone.

Well, considering that it's hard not being a mass murderer in New Vegas once you spent enough time with it, I'd say that wiping out the Brotherhood of Steel. That time I felt my character like some bloodthirsty maniac.

In my case, letting a third party person to destroy the Van Graff's was another thing. I even spared the Crimson Caravan Company, and never went into the Monte Carlo Suites. But the BoS was an order, unfortunately.

Oh, and on the side note, Cass had even more issues before the patch where the developers reduced her number of barks. Maybe you could still find a mod for that if you're on PC, I think it well worth the effort.