Is she staying inside now? I'd keep her in and do what you've been doing. Plenty of nutritious feed and drink. How does her crop feel? Has she laid eggs? Check her vent is it dirty, is it a hole or a slit? She does look muddy. I may be tempted to give her a nice warm bath then blow dry her on...
Feel the crop, is it watery or solid. Feel the feet for bumblefoot as previously suggested. Look for mites, ticks etc in feathers. Smell breath, is it particularly rancid? When was she last wormed? Does she have discharge around eyes/nose? Does she eat/drink? @Weeg