Anyone have any good idea how to handle this boss?
Her hero power summons 3 Wisps for 2 Mana. Her whole deck is cards to summon more wisps, cards to buff the board, Divine Favours and a god damn infuriating 4 Mana spell that destroys her Wisps and takes constrol of your minions up to the number of Wisps destroyed.
You need to go ahead quick and always kill her minions to keep the board clear. AoE is also helpful to swing the game. And keep your minions preferably small. But it majorly depends on your deck and passive powers whether you have a chance. Darius Crowley is easier. Houndmaster Shaw as well if you took the +2 health passive and your dogs can trade three times. But I also had great value decks and simply lost because she got ahead and I couldn't swing the board back. Sometimes she is just a counter to your deck...
Careful about her spell that kills all he wisps and takes control of your minions for each one dying. That is a brutal swing play. Basically you have to be able to play stuff very early, so you can fight for the board. If you cant, then she is a very tough boss to beat.