Oooooh, that's sad. I had same thing at my wedding shower! My future (then) SIL, let her kids get into the invitations and mess with them. I couldn't figure out why, after living all my life in a small town, hardly any of my friends came to my shower. About 2 yrs later, a woman asked me why we didn't invite her!!! I was shocked. That's when I found out over half the invites didn't go out. It can cause hard feelings........I'm sorry that happened to your niece!!!!