I have an addiction... buying fixer uppers or horses that need serious TLC. I have had so many I can't even count them, BUT I currently have one that has me puzzled. Please read the details on this mare and provide any advice or similar experiences:

4 year old mare. Hooves were horribly neglected- ran out in front of her like a laminitic horse. Thin soles with 3 mm sole depth. Cinchy. Somehow still lunges/ rode around with a lot of manners. Only signs of soreness were biting her lead rope when cinched, and slightly off up front at the trot.

Started her on a low sugar/starch diet, added minerals (CA Trace, and biotin 800 ZA Plus for a vasodilator). Put her on daily previcox for the inflammation, x rayed feet and then shoer put her front feet in casts with a leather pad and stew shoes. Did a round of Osphos. PEMF treatments.

2 weeks later, this horse is feeling GOOOOD. Too good. Not nearly as cinchy. VERY fresh on the lunge line / under saddle. I'm scratching my head- was she just in so much pain before and now she feels better so I need to work through this or?

here is her diet- pasture, grass hay, 2 qts of soaked alfalfa and beet pulp pellets, 1lb Renew gold, 2 tbsp salt, CA Trace, Biotin 800 ZA Plus.

I am inclined to agree she was just that much in pain. Sounds a lot was going on. My experience is once they get used to feeling good again, they settle down. I know from my own constant battles with chronic sonus infections, after  sinus surgery, I'll have insane amounts of energy and in such a positive mind set. It fades after a week or two, but my house and tack are spotless. It's amazing how infection/pain can just drag you down. 
Plus horses have evolved to NOT show pain for survival as a prey animal. They also learn quickly to just do what the trainer/rider want them to do so they will be left alone faster. Of course, that's not all horses, hence the quirky, bronco, aggressive labels get used on horses who have the nerve to fight back. 

I hope so, this is day 11 since the shoes and pads/casts were put on.

I bought a gelding, pretty neglected. Fungus and skin issues, 250 pounds underweight. He was so sweet and quiet. I would lightly ride him, so quiet and easy going. A few weeks in took off like a bronc which we know was possible, we think the people starved him because he was a bronc. Once he didnt toss me, he never did it again. But he was much more excitable after that.

I don't mean she'll go back to the way she was, but that once she is used to feeling good, maybe she won't be quite so fizzy. 

What would you do in the meantime / if she doesn't settle?

I'd stay consistent. Slowly increase what you expect from her behavior wise. 

I too am inclined to think she's just suddenly feeling REALLY good. If she's only 4, she was probably in this condition when she was started under saddle so she may need a fresh start with basics, so to speak.