I think Hrefena NightFeather should not be a solo boss it should be a boss that you need to go on a sidial to enter like a dungeon
You can only beat her if you can figure out a good strategy. If you are unable to form that strategy, then you my not be worthy of the spell. If you wish to explain your trouble, then state what class you are, and how you go about defeating her.
Unfortunately, all of the higher level spell quests are solo. If you need help figuring out how to win the battle, go to wizard101central.com/forums, and look up the quest.