Click your sword Icon and attack her. Raise her and she should be back to normal.

I suspect you used the polymorph self spell. I'm not sure why you can't polymorph back though.

Can anyone help me? I polymorphed Nalia into a Gnoll and now I can't change her back under the special abilities star she only has lay traps, not polymorph back. She has the stats of the Gnoll and is very slow and can not cast spells. How do I get her to change back????/

Hehe... if you weren't so desperate I'd be LMAO!! Nalia into a Gnoll!! I bet she looks better that way, too!
But let me try to help. What you should always do is keep backup saves so that you can reload the game again. I take it that you haven't done this, so I think you should try to solve this using Shadowkeeper. There is also a chance that the spell will just wear off after some time, so try resting.
Other than that, I wouldn't know. Good luck!

LMAO!!!

Hehehe, sorry.. But that was good! hehe
Well a few tips, try dispel magic, remove curse go to a temple and se what can be done, kill her and resurrect her (this is a tough one but well let her go int some traps or something..) Otherwise its shadowkeeper that would be the last answer or restart with an autosave or something..

Zazhit pretty funny. LOL. Have you tried polymorphing other again. BTW, polymorph other isn't like polymorph self, it only works once. Zats supposed to be an offensive spell. LOL Anyways, like someone else said, you could go to shadow keeper if nothing else works. But I'd still try polymorph other again first. (I just like casting spells, I can't help it.) ;o)

(climbs back on chair)
Okay. Tobbin, I'd say he's talking about a bug relating to a polymorphing item like the cloak of the sewers, since polymorph other only ever turns people into squirrels, rabbits, etc. I'd try the killing and resurrecting her. Forget traps, just hack her into pieces, she won't mind.

If you used the Sewer Cloak that allows you to transform into a troll, or jellies, etc... try looking at her innate/special abilities abilities to change back. This is marked by a star shape and is at the far right of your bottom menu. If you have any of the "kit" characters the button they use to activate their special powers is the one I'm talking about.

This happened to me with my main character. The Sewer Cloak is actually used by looking in your "satchal" or whatever that button is called, but the return to human button appears under innate/special abilities button.