Hiya ghosty - sorry you are having such trouble with dd at the moment.
I'm often out of step with other mums on these types of things, but couldn't close this thread without offering some advice.
YOu say "Wherever she is she runs over screaming and will push him away, still screaming until I pick her up." As things stand, when dd creates (screaming and pushing ds), she (eventually) gets your attention. From her POV, she is learning that if she keeps going long enough, you will give in. Therefore she has an incentive to scream and lash out at ds.
IMHO the only way to break this cycle is to ignore the bad behaviour and praise the good. Engineer a situation in which DS gets your attention, eg reading a book to him. If she kicks off, ignore her. If she starts to hit out at you and/or ds, calmly pick her up and move her away from you both, but don't look at her and don't talk to her. She will be absolutely furious, and will probably keep coming back/kicking/screaming for half an hour or more. But as long as you don't give her the attention until she calms down, she will begin to learn that she can't behave like that.
As soon as she does calm down (even if it's because she's too exhausted to cry/scream any more!), turn your attention to her. Don't mention the tantrum, just offer her a drink/read a book/cuddle/chat to her, being really positive, as if the tantrum hasn't happened.
She will probably do it several times more, but as long as you are consistent and don't give her any attention until she has calmed down, within a few days she will realise that tantrum=ignore and calm=attention.
I would warn ds what you are going to do first, as he is old enough to understand what's going on. Also, at least the first time you try this out, he is actually not going to get that much attention because you will be spending most of your time removing dd! So he needs to understand that.
Once you have established the "tantrums will not get you any attention" situation, you can reintroduce dd into the "cuddles can be shared" scenario.
Really hope this is of some help to you. I know it sounds harsh, leaving her to scream herself silly etc, but it only takes a few times of doing it for her to learn how it should be, and it won't harm her in the long run! Plus of course there is the pay-off of a benefit to everyone.