Yes this is a dangerous situation for her if the tissue is dead.
I would suggest seeing an avian vet with her to decide how to proceed.
This site may help you find one if you don't have one already.
http://www.aav.org/search/index.php
Birds can do fine with one leg and, with the danger of infection, an amputation may be what is needed if the leg is dead from lack of circulation.
Hope this helps you!
Wild Bird Expert
Rehabbing wild birds, raising nestlings, study and observation of many species