Hi @3v3ryday 🙂
I remembered reading your post not too long ago about splitting and spent a bit of time thinking about it afterwards. The concept of splitting is something that I hadn't heard of until I read your post. I have BPD traits on my list of diagnoses and had BPD as a diagnosis a while ago (which was later changed) so I understand a little about it.
What you're describing sounds to me like feeling hurt and upset that your mum seemed to not have as much time for you as she does/did for your brother, and then reacting on that hurt by not talking to her. I can understand how experiencing that from your mum might be upsetting.
Regardless of whether we are talking about a symptom of MI (splitting) or not, I think a key to managing all relationships is to recognise how emotions can impact our responses and behaviours. I know I can be very quick to respond and react to things, and often when I do I find myself in some kind of trouble because it rarely makes the situation better. I've learnt to, and am continuing to practice, pausing before responding. A recent example for me would be that I'm feeling really angry about a service I'm working with. I know that there's a good chance I'll lose my temper if/when I have to talk to them, which does nothing good for me at all, so I'm planning on communicating with them through email. This will allow me to wait a little while before replying to them, read over my reply before sending, and check whether my response is what I really want to say and not what my emotions at the time want to say. It gives me a chance to stop and check in with myself to work out what I'm feeling, think about why I might feel that way, calm down so I can think a bit clearer etc.
On a much smaller scale, an example would be when I'm with my kids. They can be pretty intense and sometimes things can go from calm to completely hectic really quickly. I don't like shouting and when I'm stressed or feeling overwhelmed around them, I notice I can shout at them. By taking a big breath, noticing that I am feeling frustrated (my chest feels tight, my muscles feel tense, my heartbeat is fast etc) and telling myself (and sometimes them) that I am feeling really frustrated, it creates a kind of pause between my feelings and my response. I've noticed when I do this, I'm less likely to shout and more likely to respond in a calmer way which ends up better for all of us.
This pause thing doesn't always work and isn't anywhere near as easy as it might sound the way I've written it, but practice helps a lot and over time it's become easier to do.
I think you said you liked writing in your last post. Perhaps you could try writing in a journal when you're feeling angry or hurt or frustrated with people like your mum? If you write what you want to do or say in your journal and then come back to it, whether it be minutes, hours or days later, checking to see if you still feel the same or if you feel differently, you might find it gives you a little more confidence that you're responding in a way that is right for you. You could also try just walking away from whatever it is that is triggering big feelings, for a moment too. One of my go-tos is 'I need to use the bathroom' when I'm around people. Just walking into another room to take a breath and a moment, can help me feel more in control of my emotions.
Hope some of that helps. Feel free to disregard any of it that doesn't right for you 🙂