haven't read all posts so apologies if repeating.
firstly, I do sympathise. I generally don't smack as I do think there are other ways, but I do believe that a parent reserves the right t discipline their child as they see fit, as long as it doesn't cause permanent injury to the child, either physical or emotional (there are other ways of hurting a child than smacking, just because you don't smack doesn't mean you're not potentially harming a child). anyway I digress...
I think it's easy as an outsider to sit and say "oh here's what you're doing wrong..", but in reality none of us were there so can't relly know how it was, but what I would say is that from your op and subsequent posts it does seem like you jumped from one solution to another to another when things didn't work. personally I find that sticking with one solution for that tantrum works better, i.e. would explain, distract, and if that didn't work would put into time-out. once I'd gone to the ignoring phase I wouldn't then go back and try and reason as I'd already been there without success.
I guess what I'm trying to say is, pick your diversion methods so they follow a sequence. if she won't listen to reason, try and distract, if she won't be distracted, then ignore, and ignore until the tantrum has run its course, yes go and ask if she's ready to behave but if she's still wining just walk away again. once you've gone into ignore mode you have to stick to that as she'll quickly learn that if she continues to try while you're ignoring then you'll divert to something else, she has to learn that ignoring means ignoring, no talk, no conversation no reasoning - she had time for that earlier.