And just so you know I defeated her in LESS then 1 HOUR (35 mins approx) and I am NOT kidding.
If you want to defeat the goddess easily all you need is 
Ryu (main character) at level 42 and have him apprenticed with bunyan as soon as you can until he is level 29 0r 31, then have him apprentice with the fishing guy for good (the guy is at the fishing spot near Rahapala just go past it and you should find that there is a ? Enter and when you have a fishing level of rodmaster or above)
HP 312
AP176
And stats of power 331
Defence 264
Int (not really needed) 98
Agility 23
And have equipped with the royal sword, dragonsheild, dragonhelm, lifearmor, soul gem and Shaman's ring.
Abilities:
Skills
Aura - learned from Ladon dragon god
Super combo - learned from bunyan
War shout - learned from Maryleep
Ward of light - learned from ladon
Holy strike - learned from Ladon
Berserk - learned from giotto the fish guy
Focus - learned from bunyan
Trump - learned from giotto
Rei level 40 have him apprenticed with maryleep, to find her you have to go to wyndia before the checkpoint above the plant there should be an inlet with a question mark (have peco in your team) there should be a pool with a rock near and 3 small shrubs before it cut them down move the rock next to thew pond, take a running start and knock it flying into the pond the fariy comes says al this stuff, tells you to find the flower jewel which is near maekyess gorge, there should be a ? Somewhere (peco in your team again) there is a tree next to the place where these two people  are talking about money and nothing else know head butb the tree, collect the flower jewel and repeat how you got her to appear first and just give her the flower jewel now you can apprentice her.
Have his stats at
HP 185
AP 68
Power 190
Defence 203
Int 100
Agl a whooping 97
Equipment, Slicer, mind sheild, sun mask, royal armor , soul gem, thunder ring
Abilties
Charm - learned from Maryleep
Shadowwalk - learned from Maryleep
Peco lvl 39
Have him apprenticed with bunyan no long thing this time COOL!!
Stats.
Power 281
Defence 250
Int 15 blee
Agility a measly 17
Equipment, Brass Knuckles, LaquerSheild, Laurel, Amber Bplate, Ring of Fire, Soul gem
Abilities
Risky blow - learned from bunyan
Disembowel - Learned from bunyan

Items needed
Plenty of multivitamins
Soul gemsX9
At least one hourglass
And one or two wisdom fruits
And have the formation chain learned from bais after you win the hide and seek game twice. To find them either look around ofr google for a walkthrough.
In the chain formation the speed of everybnody is the same as the lead character so have rei lead Ryu second Peco last

Know what you do is have rei and peco heal if nobody needs healing then have rei attack with shadowwalk and peco either physical or one of his fire or ice breath attacks, and have Ryu use accesion with INFINITY+TRANCE+RADIANCE to form a more controlable kaiser and have Ryu attack with super combo, but when his AP gets low have peco or rei heal him with a wisdom fruit. Once Ryu turns back to normal (if it happens) just have him use the Hourglass with ryu and have him attack if your lucky she should already be dead.