There are better and easier ways to do this.
1. Add both Batsprite and Batbullet to a container. Then when you create Batbullet, its own Batsprite will automatically be created. It will also be automatically picked in all events, and destroyed later when Batbullet is destroyed.
To attach the Batsprite to the bullet, use Pin behavior or add it as a child in hierarchy. Do this in the same event where the bullet is spawned.
2. You can also create a hierarchy manually in the layout editor (select both sprites, right click and add bat sprite to the bullet sprite as child). When spawning a bullet enable "Create hierarchy" checkbox - the bat sprite will be created with the bullet and will already be attached to it.