二重に呼び出さない方法。

タッチすると女の子が上に跳ねるプログラムが描きたいです。
このプログラムだとAttemped to add a SKNode which already has a parent
というエラーが出ます。二重にlet Girl = SKSpriteNode(imageNamed: "Girl")を呼び出すことになるからだと思いますが。対処法がわかりません。

class GameScene: SKScene {

    let Girl = SKSpriteNode(imageNamed: "Girl")

    override func didMove(to view: SKView) {
        createGirl()
        self.physicsWorld.gravity = CGVector(dx: 0, dy: -10)
    }

    func createSwimingGirl(){
        Girl.size = CGSize(width: self.frame.width/8, height: self.frame.width/8)
        Girl.position = CGPoint(x: self.frame.width/10*3, y: self.frame.height/2)
        Girl.physicsBody = SKPhysicsBody(rectangleOf: Girl.size)
        Girl.physicsBody?.categoryBitMask = PhysicsCatagoly.Girl
        Girl.physicsBody?.collisionBitMask = PhysicsCatagoly.Ground
        Girl.physicsBody?.affectedByGravity = true
        Girl.physicsBody?.allowsRotation = false
        self.addChild(Girl)
    }


    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch in touches{
            let location = touch.location(in: self)

            SwimingGirl.physicsBody?.velocity = CGVector(dx: 0, dy: 0)
            SwimingGirl.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 50))
            
        }
    }