Diadem had absolutely no idea why she was going along with this but if anyone asked it was because she wanted to see what Potter was made of and that she knew exactly what she was doing. Luckily, no one did, although she was sure a few looks were going to be thrown her way if anyone found out and considering his very public invitation, people had most definitely found out.
She was caught in between not going and going all day, deciding only at the very last minute, that she would show up but not before she made him sweat a bit. She would let him wait it out for a few minutes before she sauntered up to him.
It was ten minutes passed before she arrived, wearing her signature smirk and not at all portraying any sign of weakness to one of the male versions of her rival. "Hello Potter."