Is she 28 days old or 28 days from when you bred her? If she's about to kindle, did the vet check for problems related to that? She might have problems from the kits that are causing pain and preventing her from eating.
Did your vet check her teeth? Molar spurs are a possible cause. Sometimes they're hard to see without anesthetizing the rabbit for a full tooth exam. I don't know if that's possible for her at the moment.
It's good that she's at least eating something. That should keep her GI tract moving. What are are poops like?Are they small and hard, or very soft, or is there mucous?
I'dcut backon the pineapple juice because it is very sugary and could cause a bacterial imbalance. You can mix a little with water to make it taste good. Have you tried syringing plain warm water or flavored Pedialyte? My buns like the apple flavored stuff, and it has much less sugar than pineapple juice.
How's her temperature? She may feel more comfortable if you give her something warm, like a snuggle safe or a heated rice-filled sock.