Looking for some input here on some recent trends on DDs (3.5) behavior. She's in full on trying threes behavior!

1) When she goes off the rails I try to calmly talk to her but its as though she cant hear me through the madness. I will calmly try to explain to her what she has done wrong, what the "punishment" is and what she should do next time instead. Sometimes she comes out of it ok - then other times its like she is not hearing me at all. Just a complete mess. Do you just let them go completely all out tantrum until they come out of it on their own? She gets "destructive" sometimes so I default to "go sit on the step or go sit in your room until you calm down" but that just seems to set her off further. When she is in a fit I worry she will inadvertently cause "harm" to my LO (DD2 is 11 mos) - hence wanting to remove her from the situation but the step and bedroom suggestion always seem to make things spiral worse. Is this just a phase? Is there a way you have found the help them grow through this? I know her little emotions are all over the board I'm just at a loss.

2) Sometimes when she doesn fly completely off the rails (a la #1 above) she will get all sad and demand a hug, or kiss, or cuddle. I know its that she doesnt like the tone of the reprimanding and when it started I would counter it by "no, Mommy isnt going to hug you now (because I dont want to her be rewarded for bad behavior)but just because mommy takes away XYZ toy/privilege doesnt mean I dont love you any less it just means you were misbehaving by doing XYZ". But its like she doesnt even hear me. And then will sometimes slide into full melt down (see #1 above). It seems like such a double edged sword - if I give in she is getting 'rewarded' for bad behavior and if I dont I may be causing a further meltdown.

Any advice from those who have been or are in the trenches?!?!