Um Adel often absords HP from Rinoa and make she dies slowly.After that,she'll use "Meteor" immediately(this attack is not an easy problem).So all we have to do is to finish her as soon as possible."Meltdown" will be helpful in every tough battle.Give Adel some then ... unfortunately you can't attack her like crazy(^_^) - maybe your characters will unleash multi-target hit and Rinoa may as well as die (her HP now not be juctioned to any magic,so it's awfully low)!DON'T call GF,too,since any attack from them will hit
Rinoa. Ensure life for Rinoa by casting some support spell on her (Protect,Shell and Regen).Now all you have to do is to "Attack" ,only use "Limit Break" if that Limit can hit only one target(Squall may use Fated Circle or Blasting Zone -damaging multi target-so never use his Limit Break),I suggest you use Zell'Duel or Irvine'Shot(except Fire Ammo).
GOOD LUCK!