curious (bg2 spoilers)

does anyone have any tips for fighting amelyssan? my current party build is this:

Barbarian (Level 23)
Sorcerer (Level 20)
Thief (Level 27)
Cleric (Level 24)
Blade (Level 27)
Archer (Level 20)

should I export these models and go around shadows of amn once again to get higher levels? granted i've only tried to fight amelyssan once, but she wouldn't take damage when i hit her and i don't have all the great weapons that i could probably have.