Hi Concerned Dad,
Welcome to HW! Hope you get lots of feedback on your question -- starts to pick up from about this time (evening here in the UK, but afternoon I think in the USA).
Unfortunately a lot of bipolar meds are associated with weight gain -- I wish that weren't the case -- but as with all meds they seem to have different effects for different people, and very often two meds both associated with weight gain will work differently for the same person, with one causing it and the other not. There was a thread a couple of days back about this issue with lithium and I found a useful webpage that I posted in a reply, which I think mentioned that Geodon is less connected with this side effect, so this could be a very good move. Here's the thread:
More often than not you have to taper off and then come off one med completely before starting another (well, that is when they're both of the same type as these two are) -- otherwise it's like having a double dosage in the system and that can really throw a person off-kilter. That said, coming of a med can also cause withdrawal symptoms, and it's possible that this is what your daughter is coping with. My instinct says it's her being on the meds together.
You're right to call the pdoc to clarify on this: he/she should have made this clear to you before and I'm sorry that this was not done. Hopefully this incident will remind him/her that clarity in these cases is of utmost importance.
All best luck with it -- and let us know how it goes.
People are not like fish: they do not work well battered.