That is generally what we do, explain calmly that while she is screaming I cannot understand her, it works to a certain extent, but doesn't stop her from being like it, she will have another tantrum shortly after!
I don't think I expect more of her, I see what you are saying as for a long while I used to think that, but her behaviour is not great, she is either rude and abrupt, to not only me but her teachers, and other people around her, or running riot. For example, running along the chairs in a shop earlier, I got her off them and explained that was naughty, and the chairs were for people to sit on to eat, so her feet should not be on them....she screamed, threw herself on the floor yelling at me 'I promise I won't do it again' ...now if I allow her to go off again, she will do it again and laugh at me, if I hold her hand she wriggles, screams, will not stand still and will not listen to a word I say to her....so I held her hand for a few mins, she screamed, wriggled, collapsed on the floor (typical 2-3yo tantrum) and done this until we left the shop.
She can describe her feelings very well, I have always told her when she makes me happy, proud, upset etc etc, after a tantrum we have a chat, it normally goes along the lines of ;
DD : I don't like it when you hold my hand
Me : I don't like it when you are rude to me, and don't listen
DD : Ok I'm sorry
Cuddle and it's over...
She has Mummy time, without her asd brother, we also have time all together so she is not being secluded in anyway.