"What does that mean?" is a favorite question of mine, and a common one for NTs in general. Essentially asking for defenitions.
Most of the time what she comments on as "brutal" is clearly brutal, and I am usually thinking the same thing when she says it.
She is very big on following process, and not making conclusions too quickly. Seems like a P thing. Her appartment is rather organized, however. So it seems like P under control.
She strikes me more as an enneagram 8 than a 5 or 4. Not that it means for sure she is an ENT.
When it comes to typing NTs (and I fairly certain she is), I look at the problem-solving style.
Each NT has their own approach, and that approach is usually well ingrained and improved upon. That is hard for me to explain. I rely on my math-team experience, and match-up with old team-mates styles. INTJs and ENTPs have rather distinct styles from each other. INTJs like to look for some deep symbolic "meaning" to the problem they are solving (and are amazingly sucessful at finding it). I call it "inside-out" problem solving. ENTPs, on the other hand, seem to just blow through problems as if they were composed of a series of trivial sub-problems, and a few sticky points that require "break-throughs" by having "epiphanies." I call this "outside-in" problem solving. Brenan really seems outside-in.
The biggest tip-off is Interaction Style. ENTJs are In-Charge types and want to see results and see them quickly (Cam is a prime example of this style, though I think she is EsTJ who is also In-Charge style). INTJs are Chart-the-Course and plan out a way to get the results (Brennan does almost none of this and seems to take things as they come). INTPs are behind-the-scenes types, an like to work for "optimal" results (Zack was a good example of this). ENTPs are Get-Things-Going style and want to make sure there is always progress, and delegate to people they trust (this really seems like Brenan's style).
Also, I kind of "auto-type" characters and in the first episode Brennan and Angela seemed like a portotipical pair of EPs caught-up in a strange situation.