1) If you are going to air your dirty laundry on the forum, avoid specifics like names and personal details. Anyone can read here. You might want to edit.
2) You can't fire a volunteer, but you can tell her that if the group is going to continue to sponsor the activity then certain procedures have to be followed. If your group is not fully independent of the school, you can get the principal involved too. Our PTO does not handle box tops, a volunteer does it and the school handles it all. Maybe we could do a better job with a team and some PTO funding, but what they do works. If what your box top volunteer is doing is working, maybe you should not touch it. But, if you have no say in how its run, it is not a parent group program. Just clarify that piece and see what happens. If you 'fire' a volunteer, no matter what the truth is, it will look like she was kicked out for not agreeing with the leaders. Not a precedent I'd want to set.
If you don't expect too much from me, you might not be let down. <img src=images/smilies/smile.gif>