Wait, you lot are still working on her? And there's still no diagnosis? I would call you "idiots" but - well, my former boss is here for that, and has so much more fun with it, besides....!
Anyway's, well, that seems obvious enough a problem! I mean, let me Google it for "horse diseases" and get back to you, alright?
[Ten minutes later!]
No, sorry, I cannot find ANYTHING that would affect a human worse than a pony! I mean, I cannot find anything that would affect a human at all post-pony-birth....!
Although: I DO have a theory! I mean, horses tend to eat their placentas to replace blood volume and nutrients and such as, don't they? What if during the stint in Cartoon Pony land -- well - I think that it's possible that there wasn't a placenta to eat and thus- she's just suffering from blood loss and malnutrition after giving birth in that magical cartoon pony land, and then - coming back here, to the REAL world....!