I think it would have been funnier if Spike overheard her telling the "stallion" how gorgeous he was and how she was absolutely in love with it...but actually be revealed to be talking to the dress she just created and fitted onto the dummy.
"Why did you have to do that?! You call that Friendship?! THAT'S NOT FRIENDSHIP! What you did to Spike was horrible! And you should feel horrible! I cried many royal tears! You are a horrible pony!"