First of all the current notion of intellectual property rights and IP theft is a very recent invention. A change in the law pushed by bug studios like Disney to protect them from other less politically connected artists and performers who would use their material in the same way they had used what was there before them. Disney got his start taking vaudeville acts and turning them into cartoon skits. Steamboat Willie is almost 100% plagurized by today's standards. So drop the moral pretense of lawfulness on this, the law is a construct bought and paid for by the wealthy for the purpose of limiting competition. So do I pick and choose the laws I follow? To an extent we all do. If a candy machine steals my $$ I'm gonna shake the cheatos out of it. Sometimes I bring my own candy into the movies. I take a water bottle full of white rum with me into the magic kingdom every time I go. Those are laws and rules I sometimes choose to ignore because I find them unfair. If I'm caught and punished, that's a consequence I accept as part of the game. Princess parties are skating a fine line. You cannot copyright a costume pattern, and trademark protection is only to ensure that the ownership of the characters is not in doubt. Children can play Disney music at their own parties no matter who brings it. Point is, this is not nearly as blatant an infraction as panic-pants up the line would make it. But he/she's right, it is probably a violation. Tell Disney and let them decide what to do if that's what you need to sleep better at night. Then brag about what a good deed you did and watch as you are taken off all your cool friends invite lists.