You can not flip objects in composer mode.
If you are using any of the stock objects (i.e. mouth, nose, etc.) note that they are usually setup for front/left facing characters.
If you are using all your own images you can make the character face any direction you want.
Only a character/prop on the stage can be flipped.
Note: the flip function will flip the entire character and not selected parts (i.e. head) of the character.
See my CTA Tutorials on the YouTube channel CTAStepByStep
Check out EZColors for CTA. The easy way to change Render Styled (RS) colors.