She'd just lay around, not be active, just sit in the corner. If she was with other birds, they'd know and you could tell by how they treated her. They'd be gentle with her and kind of dance around her.
She doesn't seem to be in pain. Euthanizing her would, IMO, be more cruel than giving her a chance to live. I'd say keep her, let her live, let her grow and adapt to the foot. If the scales start to rub and wear, you could make a boot for her to keep it from bleeding and getting infected. Give...