There was a theory, popular among many of Gotham's costumed criminals, that all that really separated the nuts from the normals was one Really Bad Day. Or, as Joker put it, "In my case, one rotten day and a vat of chemicals."
Waking up in the insane mind of Poison Ivy was probably enough to qualify for a Really Bad Day for the personality fragment of a seventeen-year-old Lily Evans, if anything was.
Thus, the struggle for dominance between their personalities took on a far more equal turn.
Then, only a few moments later, everything seemed to calm down, and the redhaired lady patient ceased her thrashing and began to sleep soundly at last. Madam Pomphrey gave a heartfelt sigh of glad relief, then sent word to the Headmaster that everything seemed to be going fine now.
In a cot beside the treasured female patient, on the far side of a redwood tree that was now growing through the floor, Snape kept up a near constant stream of obscenities and insults directed to 'that (censored) Potter woman!' as he submitted to the fearsome itches of having his skin regrown.
He already had appointments to be fitted with magical prosthetics for the leg and missing fingers later that day, and he knew of a magical wig shop in Knockturn where he could get a bargain, but there was no way he was going to be nice about this! Even if Lily couldn't hear him, he was going to tell her off ten dozen ways at least before he even hit his stride!
Then he'd tell her off again once she was awake and could understand him. There was no cursed flytrap to save her now!
He didn't even have to worry about James.