on her 1st form use reflect on evryone and cream her with NORMAL attacks (no ODs)
on her 2nd form try using ur ppls ODs and she shuld stil hav 10 000 hp left, soo grand summon bahamut and use his OD
on her 3rd form (since u already hav bahamut out) use his OD and then use ur other aeons OD. After this she suld hav 10000 hp left soo try using water gems or fire gems...
you'll eventually come thru!
good luck <img src="/images/graemlins/smile.gif" alt="" />