well, it sounds like there is a lot of history. If anyone smacked my son, never mind repeatedly, I'd be exceptionally angry and they might well be out of my life anyway. However.
Assuming you want some sort of relationship, then maybe the best thing is to plan how much you are willing to put up with. At what point do you draw the line and walk away? you cant foresee every circumstance but you can have a rough idea, such as "we can handle upsets if they speak to us calmly but if they explode without explanation that's our limit" or "we want only contact every 6 months' or 'they can visit us, but we won't go there"
Then text her back calmly. Explain that actually you had no idea why your sister and then mother were upset and what was difficult for your family was that there was no calm explanation and chance to sort things out. If they are willing to speak in a level headed way about why they were upset then perhaps it can be sorted out, but you do need to know what the heck was going on and why they were unhappy. You left - not stormed out, but left - because you felt that whatever was happening could not be sorted out then and it was all pretty miserable. It was the best option in the circumstances.
If they respond with games such as 'you should have known' then you can only say that you didn't. They can choose either to explain in a calm way. If they don't, then keep your distance. If they do and it was a reasonable explanation then you can talk further.
If it was unreasonable then time to keep distance. From what you wrote this is not the first time it's happened and you feel that they do both twist things and broadcast them all over. If that's the case, then I'm afraid you're in for a rough ride and again, you'll have to decide just how much contact you do or don't want.
I think in all this you have to consider the impression your children are left with. Shouting and tantrums are a very poor example. For this reason alone it might be an idea to keep a bit of distance. If the good outweighs the bad, then at the least point out to the children that this is how not to handle disagreements and upsets!
I think that the keys here are calmness, speaking clearly and without too much passion and keeping a clear idea of what you want out of your mother and sister and how much you're prepared to put up with.
good luck.