I wouldn't put her back and leave her. I'd sit closely and watch.
I'm just wondering if they can help her in a way that you can't.
I'd remove her if they are picking on her.
Are you sure it's not too hot?
Continue to offer it the water by spoon.
I'd try to put it back with the others to see if the others could encourage it to eat with them.
Can you take a clear video of the set up and chick right now?
You'd have to upload it to YouTube.
Also...how did you feed it earlier? Did you have to force stuff into its mouth or did it actually eat and drink on its own?