Alright, Shuriken, it is time to break the laws of physics.
I want you to use Rapid Spin inside the pool to create a huge column/vortex of water. Then, thrust your body forward towards Ralts (keep on using Rapid Spin!), which should cause the spinning column of water to move along with you. The spinning water should easily deflect Magical Leaf, so only Thunderbolt will be a problem. To avoid it, you can either move the column of water left or right, or move yourself up or down inside the vortex. Keep on moving (and spinning!) until the column of water is right behind Ralts, and use Surf to flood Ralts out of the West Room.
I want you to use Rapid Spin inside the pool to create a huge column/vortex of water. Then, thrust your body forward towards Ralts (keep on using Rapid Spin!), which should cause the spinning column of water to move along with you. The spinning water should easily deflect Magical Leaf, so only Thunderbolt will be a problem. To avoid it, you can either move the column of water left or right, or move yourself up or down inside the vortex. Keep on moving (and spinning!) until the column of water is right behind Ralts, and use Surf to flood Ralts out of the West Room.