You can try by boosting her protein - give her an all flock/flock raiser type feed or chick starter with 18-20% protein. You can also provide her with scrambled/hard boiled eggs, tuna, salmon or meats.
Limit treats and make them a bit more "nutritional" such as a bit of fresh veggies, fruit, sunflower seeds or meal worms.
Provide fresh water (can add vitamins/electrolytes if you wish).
Offer free choice grit and oyster shell (if she is laying eggs).
Just my opinion
My Brahma hen has been dealing with sour crop for about a month and 2 weeks. She got better,but I let her out to free range way too soon. I decided she would be on a strict diet of just yogurt morning, noon and evening. She was too week to really eat on her own or even drink, because she also had mites and was anemic. So I dusted her, wrapped her in a towel and got a dropper full of yogurt and slowly feed it to her. For about 2.5 days that is all she had was yogurt with electrolyte and probiotic water. Then I got chick starter and and mixed in the water and she began to eat. Then I got rooster booster that has iron in it and placed some in her water. She is doing so much better and I am taking my time to ensure the sour crop is well on its way of being healed before I let her free range. She lost a lot of weight as well and it is slowly coming back on. I feel bad she is getting bored inside the crate and wants to get outside, but she needs time. I hope your hen gets better!