I'm rather confused. I'm not sure if this problem is due to Level One NPCs or something else, but I'm going to take a guess and think it might be either this or BG2 Tweaks' Improved Multi-Player Kick-out Dialogues, or some combination of the two.
Whenever I kick NPCs from the party I get, instead of individual NPC kick out dialogues, a different one which I don't remember getting for NPCs before installing Level One NPCs; so far as I know the Improved Multi-Player Kick-out Dialogues should only affect characters generated in Multiplayer. I'm not sure, though.
So, normally that wouldn't really be much of a problem. But in Jaheira's quest, there are a few times when she leaves the party and returns. The first time Meronia comes and asks her to return with her to the Harper Hold, she usually returns saying something along the lines of "Hail there. I said I would return, and I have.", then asks the PC to come with her to Harper Hold as soon as possible. Instead I got the same dialogue that shows when you kick an NPC out now - the same one in the screenshot above. So I asked her to rejoin the party, went back to the Harper Hold, and it was empty - no Gavalrey to ask my PC silly questions about her favorite color, sadly enough.
My Weidu.log is extremely long and I think this quest worked before I installed Level One NPCs, so if someone thinks they do need to see it I can PM it. Sorry if this isn't Level One NPCs' fault at all, like I said, it's just my best guess.
On a side note... As I'm desperately trying to avoid having to reinstall or otherwise mess around with the mods I have installed in this game at the moment, if anyone happens to know a temporary workaround like a variable I could set to make the Harpers -think- I had that conversation with Jaheira, that would also be great and I'd appreciate it.