Honestly, I think alot of it has to do with the condition. The DCS along with the seizure disorder can also cause numerous other issues both physically, mentally and emotionally. Hormones come into play with the condition as well, especially if your daughter is going through puberty or the onset of.
The best thing that I have found with my daughter is to be stern and disciplined with her, without being harsh and hateful. It was tough in the beginning, trying to cope with the outbursts and not knowing how to deal with them.
After many meltdowns of my own, i finally said enough was enough. It wasn't an overnight success, actually is still a work in progress, however I'm seeing a huge improvement in her behavior. She has rules that are required of her, if she breaks a rule she either gets grounded or time-out. Spankings no longer work as she is getting older. If I ever have to ask her to do something, I only give her two options. To do what's being asked, or to go to her room and sit until she can come out and apologize. Period. If need be, use a kitchen timer. Tell her that she can't come out until the timer goes off. As you go along, increase the amount of time she has to sit alone.
I have also started positive reinforcement. Rewarding good behavior and manners more so than chastizing the bad ones. This helps a great deal too. Something as simple as getting to play in my makeup or getting to pick a movie to watch, doesn't have to be extravagant.
Try a few of these things, give it a couple of weeks and see if anything improves. Even if it's something small, it's still improvement.
Let us know how your progress goes. I hope some of these help! Hang in there, we are all experiencing the same issues in one form or another. Have you gotten your email added to the group yet? Most of us email outside of this forum as well, drop me a line if you would like, firstname.lastname@example.org
Look forward to hearing from you!!! (big hugs)