They may want to debride the feet, or have you continue what you are doing at home if that is helping. Keep in mind that some vets who are not really familiar with chickens, may advocate putting them down for many common treatable conditions. Not saying that is what may happen, but just think...
That looks like pretty significant frostbite to me. I think she may possibly lose a few roes, but hopefully her feet will remain intact. You are doing exactly what I would do with Epsom salts soaks and Vetericyn after drying them. Time will tell how much tissue she could lose, but I think she...