Bests & Worsts Reviews from Amazon

I'm seriously confused. So: Daisy/Diana receives an email party invitation that's actually meant for a different Diana. But when she hits reply and says "wrong Diana", the Diana it was meant for RESPONDS with "sorry". So the Diana it was meant for is the one who actually SENT the email? I'm only a small fraction into the book, the two Dianas are conversing via email or the first time , but I can't understand what's happening. Why is someone sending a party invitation to themselves? I wish someone could explain this.