Sorry about your bird. This does sound like sour crop. First thing you need to do is get her under a heat lamp. Cold birds don't heal well.
The crop's good bacteria is out of balance and she now has a yeast/fungal infection.
You will need to get this gunk out of her crop. You are going to Vomit her. So hold her with both hands, one pressing on her crop, beak forward and lean her forward, beak all the way down. Put pressure on her crop. The MOMENT the gunk starts to come up, count to 2 and then lean her back upright. Any longer in this position and she can aspirate. Give her a moment to catch her breath and do this again. Get as much out of her as you can, but you will never get it all.
You will need to get some probiotics in her water. Human grade will work well if you don't have poultry probiotics. If you are using the human grade stuff, empty the capsule into a 1 quart plastic waterer, dispose of the empty capsule and fill the container with water. You will need to change this every day and make a new batch. If she is unable to drink right now, dip her beak into the water.
Feed her only warmed chopped up hard boiled eggs for several days. There is enough nutrition in these to keep her alive for quite a long time. No hard foods what so ever. You can also put some plain yogurt on these eggs for the probiotics. (the probiotics will get the balance of good bacteria back into the crop to rid her of this yeast infection.)
Vomit her each morning. I don't like to do this during the day as the bird needs to eat and drink. Keep her separated from the others and under a heat lamp. Eggs to eat only, probiotics in her water.
Here is an article I wrote for treating larger poultry, but it still holds true with quail...
https://www.backyardchickens.com/a/a-crop-story
Good luck with her and if she does get to the point of suffering, it is best to put her down.
