So I started BG2 on Friday, had Aerie in the party by Saturday morning
and have been eagerly waiting for romance to blossom. Unfortunately,
Jaheira hit on me first and I seem to have pushed the wrong buttons.

We had the talk about her missing Khalid and how there's some of him
in her despite their differences, and she said she had a good feeling about
what we had said.

I've used Shadowkeeper to check my variables: JAHEIRAROMANCEACTIVE=1
and AERIEROMANCEACTIVE=1. I don't remember the state numbers for each
of them, they were each 5-6 digits long.

I want Aerie. Have I missed my chance? Do I have to dump Jaheira from the
party to get Aerie to make a move, or can I accomplish this just by being a
jerk to Jaheira next time we talk?

I'm a male paladin, 19 charisma, in chapter 2 (clearing the troll keep right now)...and really thought my alignment would keep Jaheira from being interested...

Thanks in advance for any help.

No, don't mess.

Be nice to both of them. Tell both of them you love, don't offend them.

They'll begin to argue, then they'll ask you to choose. Choose Aerie if you want her. Tell Jaheira "Aerie's Right, you are out of line". Jaheira won't leave. Aerie will romance you!

Late last night in the troll keep, there was a brief
exchange that went, roughly:
Aerie: Gee, Jaheira, your hair is pretty in the torchlight.
Jaheira: Get your head screwed on, chick. People die in this business.
Aerie: But then we just get raised at a temple! No big deal!
Jaheira: (Tirade about loss and Final Death)

I had no input in this conversation...do I conclude rightly that
a slowly-escalating-friction thing is taking place?

(PS, thanks for the quick and reassuring response!)

This isn't a romance dialogue. It's just Aerie attempting to be nice and Jaheira clearing her up a little. Aerie has dialogue with just about everyone.