There is lots of background and I don't want to drip feed, but it would take too long and be too boring to read if I detailed all the ways I have problems with my mother.
My most recent problems are wrt to my mother and her tantrums. I can't think of any other way to put it.
I have a DD who is 3 and a half, and yesterday, my mother and I took DD to an appointment at the hospital. DD was tired and bored, and was not in a good mood generally.
There were 2 older people in the waiting room, snoozing whilst waiting for their appointment. After DD and I were called through to the consulting room, DD had a few tests, then left the consulting room to find my mother while the dr chatted to me.
About 2 minutes later, I heard DD screaming at the top of her voice. I rushed to the door with the dr, and as the dr opened the door, my mother, who was holding DD in the air by the back of her jumper, dropped DD onto the floor at mine and the drs feet and shouted 'I can't cope with this!!! before flouncing off.
The dr's mouth fell open and dr said 'Oh!' and I felt very embarrassed and didn't know what to say. I took DD to the reception to make another appointment, and receptionist was busy, so while we waited, DD had a tantrum because she wanted to run away. I took a firm hold of her hand and explained that we were just waiting for the receptionist to make another appointment, and we would be able to go. I feel like I had control of the situation, even though DD was crying, and I was holding her hand.
The next thing I knew, my mother appeared out of nowhere, and was pulling on DD telling me she would take DD. 
I felt like everyone was looking at me.
Later of course, it was DD's fault for being so naughty because she wouldn't be quiet and was waking up the snoozing people.
A few other things are that if we are out and DD is misbehaving, my mother will say 'You'd better be good DD or your mummy is going to give you such a hiding in a minute, you're going to get a belting.'
I do not use physical punishment on DD, and although mother says she doesn't condone smacking DC, she always beat smacked us, and some things she says make me disbelieve her opinion that smacking isn't a good idea.
Mother will sometimes play at building towers with bricks, or drawing, but if DD knocks the tower down, or scribbles colours in my mother's intricate drawings, mother gets really annoyed, crosses her arms across her chest, pouts, and tells DD 'I am not playing with you anymore DD because you spolit my drawing/tower etc'. Mother is serious btw. She will still refuse to play with DD if DD asks her to play something different 10 minutes later because 10 minutes ago, you scribbled over my drawing so I am not playing with you anymore.
There is so much more, but basically, mother likes to control every situation, and if she isn't in control, then she will use threats, manipulation or whatever gives her control. Failing that, she goes to extremes and throws tantrums. She thinks DD should do exactly as she says because she said so. There is no compromise. I think she expects too much from a 3 yr old.
She flies off the handle and then blames everyone else, it is never her fault. She never admits fault at all.
A few more things;
When DD was a little over a year old, she was very interested in bins. Very annoying for adults but I imagine great fun for a DC of that age.
DD had managed to get hold of something in mother's kitchen bin, so mother roared at how dirty DD was, then got the whole almost full kitchen bin, and tipped it all over the floor telling DD she could have a fantastic time playing in all of the rubbish now. The atmosphere was horrible. I was aghast, and took DD straight home, leaving mother to clean it up.
If another of mother's GC go to her house and turn the tv up and mother doesn't like it, she will turn it up to full volume so it is deafening, then ask the child 'Are you happy now?'
Mother blames me for not being responsible enough (when DD lost her glasses), not organised enough (if I can't remember something and need to find the details) and apparently I am the biggest slob in the family (because I have friends who I see instead of doing hours and hours of housework every day).
No matter what I do or don't do, mother never seems to approve of anything I do. 
She has very little respect for me, if any, has humiliated me by shouting at me in public, demeans my authority with the DC by challenging me, has told me that my friends only tolerate me out of politeness, and cannot keep anything to herself that I tell her.
If you have got this far, you may be wondering why I have anything to do with her, and the truth is, of course she is not always like this. It is only when she is annoyed and when DD is behaving, mother seems to enjoy the time she spends with DD. Some days she gets annoyed easier than others. I had a reason to cut her off completely a few years ago, and did. I then hit a crisis, and my sibling told my mother that I needed her. I didn't, but over a year had passed at that point, and I decided to give it another go, only now it has just gone back to the disrespect, back to how every single thing is about my mother, about how I should just listen to her more and I would get it right, back to how she knows every bloody thing. Arggghhhhhhhh!!!
I don't want DD to grow up to be a people pleaser, and I know she will learn from my example, but to stand up to my mother is not easy. I pluck up the courage over maybe days, force the words out which is very very difficult, and then she picks my argument apart at the seams and turns it around so I am the pathetic one, so I am the unreasonable one, that it is so hard on her, that it is silly to fall out over one incident, that I am hurting her with my terrible accusations. She then complains to my sibling about how I have said terrible things to her, and hurt her feelings so much, cries, and my sibling rings me at all hours, turns up and knocks and knocks on my door, shouts through my letterbox and asks me to once again think about what I am doing to mother, who has done so much for me, been there for me when I have needed her etc etc.
A lot of my life seems to revolve around how my mother feels, whether my mother is happy, what can be done to please my mother, yet I can't honestly say I feel she is this concerned about me. I cannot bear to see her this week, because I am still very angry over her behaviour, yet I know she will be upset that I don't go to see her. 
If I explain how angry I am, she will turn it all back to how embarrassed she felt, how if I disciplined DD more, it wouldn't have happened, how it is not her fault, and surely unless someone admits responsibility, what's the point? She just wouldn't get it IYSWIM.
How do I handle this? Am I making a fuss over very little?
I have no one else I can talk to IRL.