1.) In actionscript there is the _xscale keyword. This keyword controls a symbol, by percentage of its original size. To flip this symbol perfectly, you have to make change it to negative 100% or -100 in _xscale.

2.) So first off.. you will be working with 2 symbols, and the properties panel.

3.) Then select the ghost symbol and give it an instance name of ghost..

4.) Then go into your actions panel and select the actionscript symbol. And tell the ghost to flip. I have made it so it flips when ever you tap the keys left and right..