I too am not a WD expert but i do own a chinese water dragon. I would say go for the bugjuice and water but also see if she will take any small crix. Maybe after you get her stable take her to a vet, but if she is as bad as she sounds I wouldn't risk it now. I know a vet visit really stresses my dragon and he seems to hate me for a couple of days after. Make sure she stays warm, has lots of humidity, and has a UV light. Was she neglected or just failed to put on the weight being sickly? I know my WD closes his eyes when he is scared and is trying to "hide", she maybe doing it cuz of that or just because she is so weak. My WD has never been sick so I am not sure exactly how they act, but if she recovers I'm sure you will have a great friend on your hands.
Good luck! I hope she pulls through!