To be frank, I would just advise you to try again (but to the right address). The neighbors will most likely just throw it away, as they're probably not best friends with whomever the celebrity is; I don't live next to somebody famous, but I'm sure it's quite difficult to get chummy with them. As for the mail carrier, they definitely won't take it upon themselves to put it in the "right" mailbox.

Hi I accidentally sent a request to the wrong address. I accidentally sent it to the house next door to her. Do you think the people next door will give it to her since they're next door neighbors? Do you think the postal service will notice this and put it in the right mailbox since it is right next door?

Any help would be great.