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Party joinable NPCs will have more than one dialogue file attributed to them. In BG2 the dialogues will follow a scheme of:

Bxxx.dlg (The Banter file, where interparty dialogue is)
xxx.dlg (The basic file pretty much where the initial meeting dialogue is)
xxxJ.dlg (The Joined file, where the interjections and quest dialogue is)
xxxP.dlg (The Post/Parted file where you get the dialogues when kicking out a party member or going to re-recruit them)
xxxD.dlg (Dream file, only a couple of the original NPCs use theirs)

BG1 (originally) has the J, P, D and basic dialogues.

xxx is the tag for a particular NPC, in BG2 Jaheira is "Jaheira" so when writing dialogue for her you'll want to refer to "JAHEIRAJ" dialogue file. In BG1 (Unless BGT changes this, I only have tutu installed at the moment) the tag for Jaheira is "Jahei" so you'll want to look for a file that ends with "JAHEIJ" to add quest related dialogue there.

I say ends with - most mods put a prefix on the files they add to the game to make sure they don't override other peoples' mods or the original game content. Again, I only have tutu installed but I know the file there is called "_JAHEIJ", BGT should have something similar.

To the games Jaheira in BG1 and Jaheira in BG2 are completely different entities with different scripts and dialogues. They are not exported like the player made characters are and are not linked together.

If you haven't done the Paladin stronghold quests yet you can do that to get redeemed, one time only thing though.

Have you killed the wolf nearby?

The link in the sticky works fine, the walkthrough is second from the bottom to download on the page linked. Sorcerers hasn't been down in a long time either

Direct link to the download page is here