Bird Nibbling her Tail feathers

by Rodney
(Birmingham, UK)

Hello, I got a Pineapple Green Cheak, And she is fine in temperment and eating well, Only problem is she tends to nibble on her tail feathers until only the main stem is left. Change position of cage, Ensured constant water changes and cleaned the bowls. Is there some ointment i can put on to deter her from carrying on to stop the habit before she runs out of tail and starts on something else. Thank you