sounds like my DD as well.

well we have ahd a break through and nmow have minimal to no tantrums and are abel to reason with her :d

we did time out.
if she was not doing as she was asked or just being angry or rude we took her to her room and closed the door for 2 min.
then went in asked her to say sorry and toldher whats he w=did wasnt nice and mummy and daddy bdont like that behaviour etc

and as soon as she did it again we would say " do you want to go bakc to your room?" usually get a no answer so we say " well be nice and listen to mummy and daddy please" this usually works.

she was going to her room 3-4 times a day and now i havent sent her to her room for 5 days

we also changed her diet, we took anything containing colourings and some acids out and restricted ehr to milk water and watered down apple juice as well seems to of helped..