That text is about yukkuri Remilia which has been drawn in her invitation letters, I think. やつ means here not her, but the letter (or yukkuri Remi in it). So the text should be like "cute ones with my drawing saying Uh☆ Uh☆"
Sorry for the delayed reaction, but I think your theory makes sense. It's more likely than it being an author's note, at least. I've altered the translation accordingly.
UwaaahHeh heh heh heh. Today, there is a huge home party in my Scarlet Devil Mansion.Tell me, just how many people have gathered in my name, Sakuya?None.What?Like I said...Not a single one.But, but, we sent out so many invitations!Patchy! Patchy, where are you? Get everyone here!Those cute ones going "u~ ☆ u~ ☆"!Yes, and yet no one came. You must have a lack of virtue, M'lady.*shiver*