Most likely the pheasants will not stay with the hen, they are far more hyper than chicken chicks. Maybe for a day or two, but I wouldn't let her raise them, I think they will escape and probably get taken by a predator.
I didn't have much luck when I tried letting one of my silkies raise some ringneck pheasants. They just wouldn't stay with her and let her tend to them. I ended up having to catch them and put them in a brooder.