I do believe she is getting old, she looks like a shaver or hy line to me, and they have short life spans as they are bred only to lay eggs then die... sorry but if she keeps getting worse in colour then death will be there lurking, in saying that we had some cobb birds ( meat birds that grow to 6 kg plucked and gutted) who's comb and skin turned purple, and it kept getting worse, we ended up calling it heart attack purple. other than being slower than the others she acted like a normal chicken until one day her heart couldn't take it anymore ( about 3 months after she started changing colour) and she collapsed and died. we knew early on that she was to far gone, so we let her live out the rest of her life comfortably with her chicken friends. If it is early then don't give up hope just yet. what's her poop like? and skin colour?