It may be too late now for you to request this, if the conference is tomorrow, but I would strongly request that the school counselor be present, not just the teacher.
If the teacher is laid-back and seems to have a "kids will be kids, it'll blow over" attitude -- yes, some teachers do -- having the counselor there would ensure that another person from the school staff (1) hears everything you say; (2) sees all the things you have wisely recorded on paper; (3) knows what the teacher says and does during this meeting. This means that if you feel later that the teacher is doing nothing or his actions are inadequate, you can approach the counselor without having to start from scratch -- the counselor will already know the whole situation. Also, especially since this teacher is new to teaching, he may pay more attention to you, and to the seriousness of this bullying, if another staff member is right there in the room. Yes, I'd definitely insist that the counselor be present. If the counselor is not available I'd see if someone else (vice principal?) is available, but the counselor seems like the appropriate person here.
The teacher might get huffy or offended that you've called in the counselor, but be sure to smile nicely at him as you say, "I would like Counselor to be present because Daughter may need to talk to Counselor about how she feels, and I think it's important for Counselor to know the situation in full, so that you and she and I are all on the same page here." Don't let the teacher make you feel bad for involving the counselor. If the counselor tries to defer to the teacher and not meet with both you and the teacher, I'd tell the counselor the same thing -- my child really has issues, I want her to come talk to you, this will give you the big picture so you and the teacher have the SAME information.
Have a goal and state it clearly at the start. I would tell the teacher that by the end of this meeting tomorrow you and he and the counselor should have an action plan, which he will put into an e-mail and send to you (so you have it in writing!) by the next day, of what he will DO.
Remember that you can involve the principal later if needed. If you do not see results, I would go to the principal and emphasize that the school's own policies are not being followed and that you feel the teacher, though well-intentioned, is not assertively pursuing this issue -- however, do not threaten the teacher tomorrow with "I'll go to the principal"; see what happens but keep the idea of going to the principal in your pocket and use it if needed.
I'm a Girl Scout leader and am troubled that you saw bullying at a GS meeting. Are you a leader or co-leader for the troop? How was the bullying handled (if it was witnessed by a leader at the time it happened)? If you are not a leader of the troop, please, please be sure the leader(s) know exactly what's going on in class between these girls, not just what you saw at GS. The leaders really need to know the context outside GS if these girls have a problem in school. Good leaders should notice and stop bullying during a meeting. You might suggest that the troop consider a badge or other activity (GS has many--the leaders can ask their GS Council for ideas) that deals with getting along with others.
Most of all -- equip your daughter to deal with this "Mean Girl." Read the book "Queen Bees and Wannabes" because this other girl is a queen bee in the making. It can help you help your daughter. Also try role-playing with her what she can say or do if bullied. (Often the best response is a cold "who the ... are you?" stare and turning your back -- attention only gives bulilies what they want!). Be sure your daughter has good activities that ensure she knows she's a great person and good at things (Girl Scouts, other extracurriculars give kids friends based on shared interests and not on who's in or out at school).
Update us here!!