I'm using "split" to mean sudden intense moodswings. This is one of two ways my therapist explained the term. 

I don't know why, and I feel bad about it, but when I'm talking to my best friend, I split so much easier. Especially in an angry way. Nobody else seems to irritate me like she does and I can't place why. I don't think our relationship is toxic (it was before, but we've grown up and worked a lot on it) and we love and care for each other more than anyone else in our lives. I enjoy spending time with her as much as I do any of my other friends, and I *trust* her more than anyone I ever have. I adore her.

So, why is it so easy to get mad at her or feel depressed and anxious suddenly when talking to her? I think it's the way she talks but it's hard for me to place *why* the way we communicate is different to how I do anyone else, or why nobody else's communication style screws with me like that. My splitting isn't bad; my BPD is pretty minor, so I don't lose my shit or anything, I just get irritated or nervous. 

Please don't accuse either of us of anything. I'm just here to ask if anyone has had a similar experience.