A quick Google said that purple comb means she could be cyanotic, meaning not enough oxygenated blood is going round her system and that could be heart or lung related.
https://cluckin.net/the-sick-chicken-symptom-checker.html
Is she gaping with her mouth, sneezing or gasping? Does she have a raspy voice. I just suggested gape worm on another thread
Read this and see what you think https://thisnzlife.co.nz/signs-your-chickens-might-have-gapeworm-plus-how-to-treat-it/
When was the flock last dewormed?
https://cluckin.net/the-sick-chicken-symptom-checker.html
Is she gaping with her mouth, sneezing or gasping? Does she have a raspy voice. I just suggested gape worm on another thread
Read this and see what you think https://thisnzlife.co.nz/signs-your-chickens-might-have-gapeworm-plus-how-to-treat-it/
When was the flock last dewormed?