You are a hero! Your solution was so simple and it's works great...for the mirroring part.
Now I have a problem with the bullets and the angle of motion.
I have it like this now:
On bullet created
...Enemy is mirrored -> Bullet Set angle of motion to 0 degrees
...Enemy is not mirrored -> Bullet Set angle of motion to 180 degrees
If one of the enemies is mirrored but the other one is not, both bullets go in the same direction?
Edit: I added the "Is on-screen" condition and now it works fine as long as the enemies aren't both on screen at the same time. It would be nice if they could be on screen at the same time but it's not necessary. Thanks again for the help, I really appreciate it :)