I'm so happy to hear the Chloester is feeling a bit better. It sounds like she will have a nice full recovery.
As for whether it happens often or not. I personally think it depends on the bird. I've never had a blood feather in some of my birds, others I have had a few, and then there is Louie... About 1-2 times a month he has one that bleeds. In fact he had one last night. It only bled a little and stopped in its own so I didn't have to take care of it so that was good, but there have been many times where I've had to stop the bleeding with flour.
Leaf - 11/5/07
Louie - 1/25/08
Bill - 4/16/08
Papeete - 4/21/08