Prefab Direction - shooting

Hey! For some days I had a problem regarding one prefab direction, basically I'm building a 2D shooter game where the gun follows the mouse cursor.

My current problem is, when I'm facing right the bulletPrefab goes in the direction I want, but when I flip the character the bulletPrefab goes in the opposite direction... I tried to change it manually and it seems to be a problem with the rotation but I don't know how to solve it. Can you guys help? What I have:

     void Shoot() {
         // Obter posição do rato no "mundo"
         Vector2 mousePostion = new Vector2 (Camera.main.ScreenToWorldPoint(Input.mousePosition).x,Camera.main.ScreenToWorldPoint(Input.mousePosition).y);
         Vector2 firePointPosition = new Vector2 (firePoint.position.x, firePoint.position.y);
         RaycastHit2D hit = Physics2D.Raycast (firePointPosition, mousePostion-firePointPosition, 100, whatToHit);
         if (Time.time >= timeToSpawnEffect)
         {
             Effect();
             timeToSpawnEffect = Time.time + 1/effectSpawnRate;
         }
 
         Debug.DrawLine (firePointPosition, (mousePostion-firePointPosition)*100);
         if (hit.collider != null) {
             Debug.DrawLine (firePointPosition, hit.point, Color.red);
             Debug.Log ("Hit:" + hit.collider.name);
         }
     }
 
     void Effect()
     {
         Transform playerTransform = GameObject.FindGameObjectWithTag("Player").transform;
         Vector2 playerScale = playerTransform.localScale;
 
         if (playerScale.x > 0)
         {
             Instantiate(BulletTrailPrefab, firePoint.position, firePoint.rotation);
         }
         else
         {
             Instantiate(BulletTrailPrefab, firePoint.position, Quaternion.Euler(firePoint.rotation.x, firePoint.rotation.y, -firePoint.rotation.z));
         } 
 
     }

// firePoint is a child object