S.H.
Try to 'bond' with her somehow... when I do that with my daughter... she gets calmer and more cooperative.
Sometimes as Moms in this situation... we get in the 'habit' of being either a scolder or a punisher or an antagonist... due to the nature of their tantrums etc.
If you step OUTside of that storm.... and see her for a mere child with a tender heart... approach her that way, and try to nurture a 'relationship' with your daughter.... "bonding" with her... for my daughter, that means even if she is in a rage/tantrum... she still "needs" me, her "Mommy" and if I calm my voice and just sit with her on my lap... even if she is a big girl and just hug her... she calms down... I have learned, that when my daughter is like that... she actually NEEDS me... because she is feeling out of sorts etc.
A child... sometimes acts like that... because of an unmet "need." Try to see... how you can 'bond' with your girl... play with her, talk with her about things letting her just talk.... and openly without lecturing her etc. For my daughter, she LOVES our moments when we just talk and hang out and she can tell me about her feelings/ideas/hopes/dreams/anything. THAT for my daughter, is her 'need' FROM me.... and my not 'judging' her, nor lecturing her.
My daughter is real close to me.... and bonded.... but when she feels marginal.... because of everyday busy-ness... she acts out more. So I HAVE to, make time for her, not just "doing" things for her or with her... but FORMING A RELATIONSHIP with her... which a child needs... always everyday... not just sometimes. For me and my daughter, that means talking.... and chatting... that is how my daughter "CONNECTS" with me... and brings 'balance' to her.
So see what will 'work' with your daughter.... not when in the midst of a tantrum... but in a nice moment.... or even ASK her "WHY do you act this way? I am not your 'enemy'... I am your Mommy.... I am here for you.... but you need to tell me... why you act this way...."
My daughter is 7, almost 8. But not ADD.
Yes, the are like little PMS'ing mini women....
Next: you NEED to address her ADD condition... and research it... and talk with the Doctor..... see how she can be treated or what is best..... it is a learning curve. And for your daughter too. Maybe she even does NOT know what "ADD" is... so explain that to her. That 'label' could be something she does not understand nor know how to deal with it....
IF your daughter is on medication... maybe it is not the right meds for her... so tell the Doctor about her behavior. Maybe try another med...
And if she is acting this way in school.... you NEED to also tell the Doctor this.... so she can be evaluated...
all the best,
Susan