I would remove the dog park from the mix. Those places are not good for dogs without coping skills, and Ellie may lack those skills right now. And they are unpredictable, which you see in her reactions.
Can you simplify her life down to house/yard/immediate area around house? No stores, no parks, no outings, etc. until she learns to cope and react appropriately? I think her brain may be a little overwhelmed.
I also wonder if she has a mild seizure thing going on. I only ask because my landlords Poodle is medicated for seizures (potassium bromide), and she occasionally has these "fits". The last one caused her to run the fence and slide in the mud, over and over and over and over. Nothing stopped her until Jacky was able to catch her. This resulted in both Poodle and Jacky being covered in mud, and the Poodle getting a bath. It was like the Poodles brain had spun up and couldn't calm down. Her aggression has increased as well. She can't be out with my dogs, because she attacks one of them regularly. They used to be able to coexist in the yard.
Anyway, I wonder if Ellie's little brain is mixing signals all over.
What you describe is very similar to what Toby does, except he isn't seizing, his anxiety takes over and he stops thinking. He might run back and forth or around a certain piece of furniture repetitively while barking, or he might spin and wine. Either way he won't stop until someone is able to catch him.
Some times when the dog has an extremely stressful event, it can take days for them to recover. This sounds like what's going on with Ellie. During a time of stress they release stress hormones, which can take days to leave their systems, especially if they were extremely stressed.
Reducing Ellie's exposure to the outside world sounds like a good idea. No dog park is vital. For exercise either go somewhere very quiet that won't cause her any stress or stick to your yard.
Personally, I'd look into natural remedies before medication. You may want to try going to a natural vet, who may have more non chemical solutions for you.
Training is number one, which you've done thoroughly. You should pat yourself on the back for that one, so many people would have given up.
Natural medicine is next. Rescue Remedy has been helpful to us but more than likely won't be enough for severe anxiety and aggression.
Like I said, L-theanine has done wonders for Toby. If you're not comfortable using the type for people you can buy the name brand made for dogs.
http://www.virbacvet.com/Products/VirbacAnimalHealthBehavioralHealth/ANXITANEChewableTablets.aspx
If you do try the type for people, don't buy chewable, it contains xylitol.
