I started a thief and got up to chapter 3 then at night that stupid vampire lady comes out and beats the crud out of me.What can i do to waist her and her minnions once and for all? any responce will be helpful.

Have a Priest/Druid cast Negative plane protection on your best fighter(s) and send them out as scouts, then bring in everyone else once they are focused on your fighters. That's probably the most straight-forward way to try. Of course, you could use summoned monsters to soften them up a bit as well.

Almost forgot... (SPOILER?)
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if you are in chapter 3... if you have a character that can use the amulet of power (from Aran Linvail), try to beef that character up as much as possible while using the amulet - it has Negative plane protection.

Also, use Scroll of Protection from Undead on that person.