There was a particularly good Ent character played in the Green Dragon (our free form 'pub' RPG in the Shire RPG forum) some months ago,
and she was an Entwife, too. I cannot remember the name of the character off the top of my head, but she may have been in the Green Dragon sometime around page 20 or so...
It's interesting thinking about whether such a character would be canonical or not. Tolkien created the Entwives, but he did not go as far as to actually present us with one. Would it be acceptable to assume what the character might be like? I think it might be, as Tolkien after all hoped that others would come after him "wielding paint and music and drama".
Maybe an anarchic Entwife would be appropriate? It could be a return to the concept of the Wildwood...she could have the character of Old Man Willow perhaps?