The Feminum Mystique: Part 2 - S1-E6
Continuity mistake: When Wonder Woman is spinning the XPJ-1 around, she's seen approaching the jet with her hands empty and her lasso on her side where it usually is. As the scene progresses, her golden lasso magically appears in her right hand even though she never reached down to pick it up.
Answer: The transformation twirling was invented for the 1970s TV series only, to explain her quick change from Diana Prince to Wonder Woman. However, it would have been nice to do a little spin homage in the movie.