I have a dying kitten, don't know what to do.?

I have two sister kittens last monday (Charm and Strange). My friend found them. Maybe the mom was around and she shouldn't have picked them at all, but in any way, she took them home. She got tired of the kittens meowing after about two days so I accepted to adopt them even though I didn't know anything about raising kittens. They were aprox. 4 weeks old when I got them and one of them was a runt (Charm). On their 5th week (yesterday), I woke up and Charm, the runt was laying cold on the ground, I thought she was dead but then she meowed a little so I rushed her to the hospital. They put her in intensive care and force fed her and I picked her up later in the day. The vet was very generous in cutting down my bill when he realized I didn't have much money and I indeed spent all my money paying him. Today she hasn't eaten much and is very lethargic. She's clearly dying, she is less than half the weight she should be and vet said her organs are probably underdeveloped and won't survive.