here's some advice for the final boss.
1. the ruby only deflects light blue attacks apart from the meteorite
2.the meteorite attack takes 2 turns to acttualy hit you so use the first turn to attack then the second to heal right before the attack hits you
3.the most powerful attack that esix has doesn't actually one shot you it deals 50% damage so you should not use the opal if you have 100% hp because it will come in handy when you have almost beaten her
4.if you don't use the opal on her strongest attack then if you know a move will kill you use the opal then imeadietly attack if she is close to death. the only time you should need to use the opal is if he uses the move with the ghost animation or the meteorite. I CAN'T STRESS THIS ENOUGH ATTACK WHEN SHE CHARGES UP THE METEORITE THEN HEAL THE TURN BEFORE THE ATTACK COMENCES.
5.every item you get will be of use in the fight so be sure to get a lot of rope and wood in the first half of the island since the microchip technicaly doesn't exist so you can't run out of energy and get a lot of lemon pies from the baker cat since they're unlimited i'm pretty sure
6.when you get back to the first half of the island before going to fight the boss in the temple where you got the ruby from go visit the cat's other than the litten. there will be catnip and lemon pies where they used to be and in the case of the digimon there will be 20 wood and 20 rope where she was
7.get a whole buttload of silent flowers since you can use them for a verry powerfull attack in the fight but you should only use the attack when she uses the move recover.
8.the topaz will block yellow attacks the saphire will block light blue attacks apart from the meteorite and the ruby reflects light blue attacks and blocks the red move: charge and the opal blocks all
Hope this hellps you