I hope it's ok to post here, I've been a lurker for a long time. I just wanted to address @Theydontwantme as some of the issues around your mum resonate with me. My own mum was similar when I was growing up in terms of not being able to deal with emotions, especially negative ones - she'd simply just shut down. Or get angry that I even wanted to talk about a difficult subject with her. It caused me to become incredibly withdrawn as a child and I learned to bury my emotions so as not to feel like a burden. I'm only now unlearning these behaviours in my 30s.
I strongly suspect my mum is ND but she also almost certainly has CPTSD from an abusive and emotionally neglectful upbringing - her own mother was monstrous which I only found out as an adult. I think this is at the core of her inability to deal with emotions and understanding that has really helped me process my own trauma and see her behaviour through a different lens. She just couldn't go there and shut down as a coping/survival mechanism she had to develop in childhood. She showed love in other ways, sometimes misguided, but she was traumatised as well as possibly being autistic. It allowed me accept that she wasn't able to be the mum I needed but that it wasn't my fault or my job to 'fix' her. It also allowed me to feel empathy for her as a complex, multifaceted human, and not just think of her as a mum.
A life without emotion would literally kill me
I've quoted what you said and I wonder if it would be helpful to reframe this from your mum's perspective; what if she feels like a life full of emotions would kill her? Because it triggers past trauma that's just too painful to bear. Or if she is autistic, because deep emotional connection is actually incredibly overwhelming and not something she's wired for. You compare yourself to her quite a lot and think because you have ADHD and she might be autistic that you should be similar but that just isn't the case. As mad is it seems, your (perfectly normal) need for meaningful connections and support in hard times will be as alien to your mum as her total avoidance is to you. None of this negates your own pain at all but perhaps it might give you an understanding that it's not anything you have done to make her behave this way, and allow you to accept that she will never be able to give you what you need. Ultimately, if the relationship is causing you distress then you need to go NC or at the very least stop reaching out for to her for support hoping it'll be different.
A mother wound is so profound but if you have people in your life you fill you up and 'get' you, put your energy into those relationships. I'd also really recommend EDMR as a way of working through your trauma. Talking therapy and CBT aren't always effective if you're ND and you seem to be stuck in a perpetual loop of rumination.