LOL as any good parent he used guile to set you to (what he thought to be) the right path.
But from a roleplaying perspective I think you can find a reason to dump her -and Khalid... or you cheat!

What I always when removing NPC from the party is:
-I make sure their spell selection is appropriate for a generic encounter.
-I refresh memorized spells with a good rest.
-I give them tolerable quality equipment (that I don't need of course, generosity goes so far)
-I kick them out in a tavern (in lieu of mods that send them there on their own)
-I tell them it's for a little while and to wait. That I later "forget" is completely irrelevant.

See? No teeny bit of guilt.

Jaheira is probably my favourite female character in BG2. She is a bit of a bore in BG1 though, and not too useful to boot, so I can understand wanting to kick her out in that game.

You could always 'accidentally' put an arrow or a sword through her gut.... :p

I'm going to use her and Khalid as tanks and drop her when she dies. How will this work with BGT and going into BG2?

I believe with BGT installed she won`t be in the cell in Irenicus` dungeon if she had died in BG1.

Excellent.