I think it shows some spunk that she comes up to you.  LIke other posters have said,  isolate her  with one friend, or even none if you think she is contagious. Maybe group activities  tire her out. When they aren't thriving I think that it is okay to spoil them. Carry them around with you (maybe in a deep  jacket or apron pocket, let her lay on your chest when you watch tv.  They get warmed by your body and the pocket makes them feel safe and close to mama(you).  You really can't go by charts and schedules of how much she should gain in a day or whatever., every chick is an individual.  It's best to go by their actions.
You might want to put a little box inside her enclosure so she can go to her cave and feel secure. A mirror is good so she will think she isn't alone.  A little stuffed toy to cuddle up with. A feather duster so she can hide under mama's wings. Will she eat anything off your finger?  Like is you had yoqurt on it.  Maybe just open her beak a tiny bit to slip some in.  Once she tastes it she may decide she likes it.  Or finely mash some egg yolk for her. Does she know how to drink and where the water is? Maybe she has some vision problem  apart from, or because of her goopy eyes.  The terramycin eye ointment should help her. Just don't let the tip touch her eye - you want to keep it sterile for other chicks, etc.
A friend is good but if she isn't feeling up to par and the friend is energetic, that will take a toil on her . Would she take a little gro gel, or sugar water? How old is she? 
I always feel if thee is life, there is hope.  The little stinkers that show attidude, pecking, etc. have a better chance of pulling thru than the quiet, sullen ones. Please keep us posted.  Can you post pics. of her and maybe with a hatchmate, so we can see the size difference?  She may just be a smaller, slower growing chick and not require as much food as you think or eating something on the sly, if she is in with the others.  Please keep us informed. I am subscribing to this thread to hear how she does.