CECIL SACRAFICE FOR THE PINK TAIL Equip Cecil with the onion sword, crystal armor, crystal shield or onion shield if you have it, a crystal ring(steal it from the red dragon with edge) if you don't have that just equip the protect ring, then the ribbon. Set his abilities so he has darkness as the auto battle command, then set draw attacks, kick, and treasure hunter. So when the Flan Princess attacks you you will counter with kicks and do more damage all around making the battle end quicker and you also save money from stardust. Most of the time at the end the Flan Princess will drop an ether or elixir so you can give that to rosa after her mp runs out from using arise on Cecil after each fight. I also am very confident that you will get at least one pink tail if you buy 99 sirens and keep fighting without turning off your ds or reseting.
It's quicker because the flan princess loves to attack and everytime they attack cecil kicks them and with darkness he does more damage all around. then if you have your other chracters equipped with the best weapons the fight will be over real quick.
Also it fits Cecil's character to be noble and sacrafice himself for the other members in the party. If you got him up to level 99 with full stats he'll do a lot of damage. Try it out. It only takes me like 30 to 45 seconds tops to finish the fight.