I think her blatant disregard of history and facts to suit whatever dumbass point she wants to make is the most offensive thing to me
That's part of it for me. The part that really annoys me is how Brianna 1) never shuts up about anything; and 2) tries to sound educated by having an opinion about everything, ever stuff she doesn't fully understand. She yammers on like a lonely senior citizen that lives at home alone, but whenever they're out in public, they start talking about stuff no one was asking about and about things they've only seen on cable news.
The main difference however is that unlike the lonely senior citizen, Brianna has a small cabal of bug-eyed mouthbreathers that will listen to every word she says because they feed into the "oh she's so interesting and brave" mindset because they need a martyr to follow to feel better about themselves, and instead of trying to dedicate themselves to following someone that is actually trying to change the system and they would have to reevaluate their own lives, they decide to glom onto the K-Mart Blue Light Special equivalent of activism which state you can still buy all the worthless shit you already do and do nothing that would get you outside your comfort level, but all you have to do is be a whiny little shit and make everyone else's life difficult that doesn't fall into your tiny little worldview.
Brianna has created this circular logic train. If you're a white cis male, trying to explain your position is mansplaining and demeaning to her if you're someone to suck up to, she's willing to backpedal to pat their ass, but will never actually say, "Oh, I was mistaken." She has to always be right, and if she can't be right, she changes the conversation... which is probably why she has like 20 different conversations in a day. And her cabal is all too happy to stand by, nodding like a bunch of simpletons. However, the more Brianna yammers on, the more and more the cabal wakes up and realizes she does nothing but talk and insults everyone's intelligence.