I agree that there is some keratin present which leads me to conclude that the growth was a keratinic horn originating from the skin. The fast growth rate usually does indicate malignancy and so I think you did the right thing. If you don't wanna eat the egg, microwave scramble it and give it...
I would let it scab over and release her back with her flock. You can put cornstarch on the bleeding area and it will help stop it. Corn starch is a proper substitute for styptic powder. It may be cancerous, maybe not. Either way, it's not contagious. Just watch her like you would your other...
http://www.nejm.org/doi/full/10.1056/NEJMicm075948
I'm only familiar with human nursing and can apply what I've seen in human's to what is seen in other animals....sometimes.
The growth reminded me of a keratonic horny growth. Good luck with your bird. If she seems happy and healthy, I'd leave...