I'm playing as a sorcerer and have the dwarf thief as a companion, hell hound as a familiar.

Long story short, I killed Tymofarrar, then go back to J'Nah. I have to fight her. I use the powder on her, which takes her to "injured." From there I get killed no matter what I do. I run and try to let the gnolls kill her, but they all get killed and eventually she kills me and both companions. I've even set the difficulty to easy, and I can't damage her at all, no matter what I do. Sh is impervious to my magic and 1-2 hits from her and I'm dead.

Any ideas? Is playing sorcerer just really, really hard? I have had a pretty easy time up till now.

Help please. Thanks.

Look through any items you've picked up and see if any have abilities that can help you (I think a few can be used to summon a bit of additional help). If you're finding your spells aren't able to overcome her spell resistance then you could try hitting her with a few weakening spells first (such as Lesser Spell Breach). You could also try buying some scrolls beforehand to supplement the spells your character knows.

In order to reach J'Nah You had to smite four elementals. The potion (and even moreso the cloak, if You figured out the puzzle) You acquired along the way are very useful when fighting the demon fey.

Bring her wards down with Dispel Magic and Lesser Spell breach and proceed to unload Your offensive spells at her.

This is pretty cheap, but when you approach her, you'll notice she'll start to head toward you. By backpedaling a bit you can lead her away from her goons. This can be a short distance just to give you an edge, or I suppose you could even lead her into the hallway if you're really having trouble. It's not wonderful, but when you're in your first SoU campaign, it can make life easier.