After she gets the package. If the post staff just break into your house to take your stuff based on internet communication, they'd find out about your ring the next time one of you mentioned it, among other problems.

I presume email, and that GP misspoke when they said "model" and meant a file that the key could be modeled and printed from. That being said, that solution definitely skirts the intention of the puzzle, but would certainly work given the restrictions the puzzle did list.