[header] How to play fight with your girlfriend [title] Initiate the fight. [step] Start by playfully pushing or bumping into your partner on purpose. Whether she's concentrating profusely on a task, or just simply standing idle, approach her and nudge her gently. 
Carry on with this action until she responds with either pushing you away and telling her to leave her be, or she joins in on the fun. Either way, do this in a style that shows you're only clowning around and want her to participate-she'll hopefully get the gist and engage.