even tho i still have problems with hunters i can beat them finally after many many defeats hehe. A hunter is basically his pet, and especially if you're a caster class and the hunter has a "normal" pet (as akasha said with a 2.0 speed) then the hunter's technique is, sent the pet to the caster, dont let him cast even one spell and kill him while at it. If you're demonology i would suggest this series of actions:
1. Summon Voidwalker/Sacrifice for the bubble so you can cast when she sends her pet/Summon succubus
2. Fear her incoming pet and send your succubus to seduce
3. Give her a Curse Of Shadows/ send a shadowbolt and try to chain it with a new seduce as soon as it hits
4. Re-fear her pet and keep seducing/nuking/fearing her pet until she's dead
Of course trying to slip in a few dots while doing all this would just make the whole deal faster and easier for you. remember the point is to keep her pet feared/away from you, and not let her trap you.