At this point, it may be easier on her if you just dub.
Just be sure to keep her as calm as possible during the procedure, and have a good "quick stop" bleeding powder on hand. Since it it very cold out, the bleeding should stop fairly quickly. In the summer, birds tend to bleed a lot more due to the increased blood flow because of the heat.
Other than that, make sure you have a sharp pair of clean scissors and someone to hold her very still. Typically the procedure is very quick and the birds should heal quickly. Just watch out for infection. With that much frostbite, it would be more painful for the comb to fall off on it's own than it would be for a quick dub.