What makes you think this is not a real half dollar? The design looks fine and the weight is about right for a circulated Walker. If it were really made of copper alloy (i.e., brass) it would be quite a bit lighter than 12.23 grams.
I'd bet it is a real Walker that had been plated as a novelty item and the plating is mostly worn off. It's certainly worth at least $6.00 or so for its silver melt value and a collector might pay a bit more, given that the 1928-S is a slightly better date.
I'd be happy to reimburse your friend for the fifty cents plus postage if she wants to send the coin to me!
