Did the crop go down? does it smell sour? It may not be hard, but is it mushy at all?
What antibiotic are you giving? If you are giving anything ending in "mycin" or "cycline", do NOT give yogurt. Dairy products are contraindicated for those medications.
Yogurt acts as a "probiotic", something containing live, beneficial bacteria. They're necessary for any ill, stressed, and medicated bird daily until the bird is healthy again.
If you're using cyclines or mycins, try acidophilus capsules/tablets from the grocer/pharmcy/health food store vitamin section. Or use livestock probiotics. In the latter case, make sure the label says they contain live probiotics and not just byproducts or fermentation products. Live bacteria in livestock probiotics will usually appear as a number and CFU.
If you're not using a cycline/mycin, use yogurt instead. For a full sized pullet, 1/2-1 teaspoon daily. It's essential that the good bacteria are replaced. They're literally the workers that feed your bird.
If the crop is still full (and sour) then you'll want to empty it. She needs nutrition. You can mix yogurt, applesauce (babyfood applesauce since she's so ill), a boiled mashed egg yolk (freeze what you don't use), and her crumbles/pellets wetted to where they fall apart but aren't to wet. Try feeding her that. You can also add a little pedialyte or honey or karo for a day to get some fuel into her. But usually the applesauce is tempting enough for them.
If you can get her through this, I wouldn't worry so much about permanent damage. She's just too weak to eat.
By the way, check her carefully all over for lice/mites. they're nearly microscopic. Also check her vent for any redness or anything on it. Mites/lice will often hang out there and love to lay their eggs there near the vent on feather shafts. Anemia from mites/lice can take a bird down this quick.
Use the fluids you're giving her to get nutrition in her. That "glop" that I described above - you can put a little in the water til it's just barely thicker than water and use that to hydrate her. That way you're nourishing her an dhydrating her. Hydrating her alone won't help her to stand and return to normal.
I hope this helps as a start.