I personally love all seasons here so I can't give her a proper advice...Any recommendation?
Personally, I recommend Spring when the cherry flowers are in fool blossom and Autumn when the leaves change their colour.
But if she wants to see snow also winter is good!
I lived in Kanazawa and I recommend Kenrokuen when it there's snow.
It's safe not to wear high heels when you go there, especially if it already snowed...Your feet become sloppy and there's the risk you slip and fall so pay attention.