tldr; To flip or mirror a group of sprites, take the parent gameobject, rotate it 180 around the y axis. All the children attached to it will rotate as well.
I wanted to flip or rotate or mirror a sprite that was composed of a group of child sprites. Selecting flip on the parent object's renderer didn't seem to work, or rather it flipped that sprite, but not all the children.
In a script attached to the parent object I called:
transform.Rotate(new Vector3(0, 180, 0));
This rotated the sprite and all of its children, so now the entire sprite was facing the opposite direction (right instead of left) . The animations associated with the sprites were also flipped correctly.
