Girlfriend skinny?

So, I went to lunch with my girl yesterday and this is what is said under the chocolate mousse.  What does it mean?  This will keep you girl skinny?  Does it mean if your girl is skinny she CAN eat it?  And is it or is it not girlfriend?  Not Girl Friend?  Oh by the way I'm not picking on this place, I happen to love their food and service.  I hope that it's the funny one....that if your girl is skinny, THEN AND ONLY THEN CAN SHE EAT THIS...Laugh out loud!!!!!!!  That would be amazing!