The first battle against Edea is scripted and the player cannot get Game Over, but defeating Edea will grant the party some AP. If the player is about to lose, Edea will unleash her Limit Break in an FMV and the player will not get AP from the battle. The battle will end the same regardless. If the player takes too long, the battle will end automatically in the party's defeat.
Edea casts all three -"aga" level spells, easily dealing over 300 damage, and can cast Dispel to rid the party of any positive statuses. One can exploit this tendency by repeatedly summoningCarbuncle to cast Reflect on the party forcing Edea to either waste turns dispelling the Reflect shield, or to settle for using her Astral Punch physical attack, which is weak.
Defeated... useless fool. Enough play. SeeDs must die!
—Edea, after Seifer is defeated.
Second time around Edea's spell list has increased drastically, focusing around the core spells of Blizzaga, Death, Silence, and Maelstrom, which halves every target's current HP and inflicts Curse preventing the party from using Limit Breaks. On top of that, Edea will cast Reflect on herself and can still dispel any positive effects on the party. She is vulnerable to Sleep.
The player should junction Blizzaga and Firaga to Elem-Def-Junc and Death to Stat-Def-Junc to take care of three of Edea's most powerful spells. Junctioning Pain to Stat-Def-Junc will protect from Curse and Silence. If the player hasn't got enough Pain magic they can junction Silence instead and equip the Draw command to draw-cast Esuna to rid of Curse, or use Siren's Treatment command. It is possible to make the party invincible with the right junctions by making Maelstrom the only way Edea can actually hurt the party, which can only halve HP, but never kill. If the party is protected from Curse, Maelstrom will make Limit Breaks easy to obtain. If not well protected, one should take care to keep HP up, as Edea uses Maelstrom frequently.