I don't get why these women are so fixated on whatever comes out of Brandi's mouth by now. Her motivations, like the thoughts expressed, come from such a shallow place, and you just can't take her so seriously.
She doesn't mean much with most of what she says, until you come back firing, and then she feels license to get ugly back. The whole "stop picking on me" on her part—I think—comes from her lack of understanding that she actually started it. She doesn't get (and for some of these things, neither do I, if I'm being honest) why it's worth spending all this time arguing about something that she spent literally not one second thinking about saying or doing. Should she take a second and think? Sure, but they know what they're getting from her now and can stop clutching their pearls at her already.
Also, in context Brandi obviously said "watch your back" to Lisa about trusting her relationships with the other ladies, especially Kyle, so let's step back on the suggestion of a threat there. The whole "I've beaten you up in my head a hundred times" thing is ugly, but hardly an indicator of anything other than a vivid fantasy life.
So much of the conflict on these shows seems to come from the participants' lackluster communication skills. Seems if they could just express themselves clearly, they'd have less to argue about. Poor ol' burbly Kim trying to compare her selection of gigs with Lisa Rinna, and trying to say—because she did finally say it that way, even though by then the catty umbrage had already started and it got ignored—that Lisa would put herself out there more than Kim. Not in an "I'm so special/accomplished and you're such a sellout" way, but in a "you're way more adventurous than me" way.
Kyle likes to use the "my sister" thing like it's some kind of magic talisman that heals all wounds. There are plenty of siblings who aren't that close and don't get along for many reasons valid or otherwise. Being raised with another person is not a guaranteed passport to lifelong relationship intimacy, and shouldn't be used as a club to try and force it.
I'm not team Brandi/Kim in any way (because they're obviously flawed people who'd be tough for anybody to handle day-to-day), but I just don't get the hysteria or the need to treat every catty or nasty comment as such an atrocity.