Why is my mother like that?

I have a complicated relationship with my mother. Example, I prefer to live in a different country all alone but not to go back to her despite she would be very happy.

She has always shown this trait of cruelty which, as I discovered with time, hides a meek little girl behind (she won’t admit, she’ll attack). she pushes the buck on anyone and anything for the rows, broken relationships, etc but never admits a mistake. She could never genuinely say ‘I'm sorry’. She drilled my dad’s brain with pretty scary rows (for us kids -I’ve a brother - to observe in the middle of the night), and insults (especially after they’d come back home from parties involving alcohol; yes, alcohol turns her into an evil substance). When we grew up, my dad left.

Everyone seems to be living a life except her, she clings to her old bad job, isn’t searching for anything new and nags, nags all the time. She talks bad about everything and everyone without really trying to understand people and their pains, and when I confront her on negative attitude, she lashes out on me in a hysterical way that leaves me scared to death (that she might have an attack or something).

She fails to support a conversation with the closest people she has: my dad, her own sister and myself; we noticed that with us she just goes randomly from one thought to another without even bothering if her interlocutor understands her, if it’s interesting or if it’s relevant at all. When I say gossip is not my buzz, she won’t hear and plain continue! It’s as if she’s physically there but mentally elsewhere, very eerie weird effect to observe.
And when she has had a drink, plug your ears and run.. but you know what? With people she relates to much less she can have an interesting conversation !!

When she has an opportunity to develop a scandal, she takes it, when she doesn’t , she’s miserable. Recently, she’s got involved herself in a strange activity of purchasing unnecessary stuff and stocking it up at home with the money she really needed to pay for other things. Then she would say she’s run out of money and life is very difficult. I used to send her money but with all the crazy economic volatility around, I have been passing through my own roller coasters, and as of some time ago, couldn’t send her as much as before.

I was very hurt to know that she used me by crying about her difficult life and then going and spending the money I had sent her on some stuff stocking up she won’t be able to use up alone in the next decade. She won’t resell it as clear as day. (To explain herself, she said she has been investing in something (she couldn’t explain in what to anyone and stubbornly kept it secret), with the purpose of paying the dividends to us, her children (I have a brother). I told her best investment would be in her own health and high morale. She had another a lash out of accusations on me...

To give my mother credit, she is expert at her work (she is cardio rheumatologist), she loves her work and lives by it, her patients love her. (Something tells me they wouldn’t ever imagine what she is like outside work.)
And yes, I understand that it is tough for her to live alone. but she does nothing to keep her friendships!. I mean, we - her children - cannot substitute the whole world for her, right? If neither of us has kids (she dreams of grandchildren because most of her peers have them), she feels inferior and gives us that depressive hysteria on the subject. But what do we have to do with that? This is an enormous pressure. I mean I don’t oppose and am willing to go into family thing but it’s not something to order on amazon ..

My cousin told me it’s my cross to carry in life but I’ve been wondering why. It’s not my cross, I’ve worked for two decades since I left home to pump up my energy and reinvent myself piece by piece. I’ve changed. The idea of going back to her (need be), though, still scares the hell out of me, to the degree of panic attack. I want to direct my energy into my life and maybe have that very wonderful family of mine instead of catering to my mother’s energy sucking activities. It sounds bad but I have only his much energy to manage in life.

If someone can clarify something about my mother from scientific/psychic viewpoint, why she is clinging to the past without growing out of it, what is she missing/lacking that no one mistakenly notices and she doesn’t have the skill to explain herself.. something is awfully wrong and with time it’s deteriorating, that depression of hers.. Are there ways to get through to her common sense? To stimulate her positivity because that’s all what I would want from my mom, - think and feel positive. She says she is trying but then slides back again.. can I help her at all?

Thank you for reading this long.