Well you don't just face her alone, she has two bodyguards (both heroes) Ghrenis the Vicious and Ansert the Deciever who protect her at all times, for the majority of the map you will have to destroy 3 bases which all have a pile of bodies in the center, you will have to go and burn those, after all 3 are destroyed, dioneve along with her bodyguards will appear in the back center of a map, near a particular cemetary and she will raise a whole host of shit against you, you have to go and defeat them, when you do she will get angry, and invoke a special spell that will burn the whole map, thus you have about 3 minutes to get your hero to a exit point in the south of the map
at least that was the plan, and we've only gone around to making the terrain of the map so far