Nevermind lionz, I figured it out. For future reference, this is what I did.
Even though the bullet: set angle for motion, says angle, you still need to type angle. So put angle(main-object.X,main-object.Y, receiving-object.X, receiving-object.Y).
So now the bullet will head towards the sprite/object you want to receive the bullet. If you reversed the main-object and receiving-object, the bullet will go the opposite direction.
Oh, and don't forget to turn off set angle in the bullets behavior box. And make sure to not use or delete any events that use rotate to (receiving object) or set angle towards (receiving object). Just use the steps above.