Temper tantrums can be scary things for toddlers. No matter what has caused the tantrum, she is showing that at that moment she does not have the ability to regulate her emotions. She is not behaving, but rather responding with pure emotion.
It will help to soothe her back into herself, and also prevent her from accidently harming herself physically, if consistently with each big tantrum you calmy but firmly pick her up and hold her in your arms for the duration her tantrum. Rock her in your lap, held snugly, or my son responds best to holding him on my front with legs around my waist and his head over my shoulder, then walk and shuuushh, just like when he was tiny.
This is not the time for discussion of the problem that caused the tantrum nor a time to use many words when speaking to her. You are in the role of soother. This allows her to that she need not be afraid because the strange out-of-control feeling of the tantrum will end, and that she will have you to help her regulate her emotions until she can do it on her own. :)