i'm sorry your having so many potty problems with tink. As i was reading i was gonna suggest more crate time even when your home but then i read you tried that for two weeks and she screamed constantly. I really don't know what else to offer you in the way of advise because consulting a behaviorist. But then again maybe she does have some brain damage from the seizures and just doesn't get it.
I'm sorry.
Maybe if you do diaper her all the time she'll hold it because she won't want to go in her diaper and then sit in it, ya know?