Hello, I was curious how your hen made out? I have an EE with the exact problem, there is very little info on this specifically and I assumed she had crossbeak. Her tumor is so large, the bottom beak is actually curving in on itself(kinda of like when you roll your tounge) and I can't see her tounge anymore. I've tried everything, and I'm losing this battle. She is the same as your hen in every way you mentioned. So outgoing, following me everywhere, riding on my shoulder. I will miss her as I fear she won't last much longer.
Any info you could offer might be helpful, considering your experience. Thanks - Jess