After expanding, get transformed by Dr. Puzz. The MollyCool is on top of the lighthouse. Head over to the non-land area blocked by boulders. Clear them away to meet someone in need of a back scratch. After obliging him, the battle will start.
The battle has 3 phases. Begin by aiming for the craters with the opposing weapon, while trying to avoid its attacks. If it shoots ice, use flamethrower. If it shoots fire, use snowballs. If it shoots rocks, use grenade launcher. Once all are gone, a barrage of meteors come down, just drive in circles while boosting to avoid damage. The next phase is similar to the first, except with meteor attacks as well. The last phase is the easiest, just shoot whatever you want at her face! If you time it right, she won't even be able to counterattack! I preferred the grenade launcher due to the rate of fire and attack distance.