Here is what three days can genuinely do, and what it cannot.
Short answer: in three days, you cannot remove a tan. You can even out the skin, moisturise it well, and let your artist match the neck to the face. That combination works, and it is what professionals do.
Cool shower. Moisturise the face, neck, ears and arms properly — dry tanned skin looks darker than moisturised tanned skin. Sunscreen from now until the wedding, including on the neck and the back of the hands. Stop it getting darker. No sun for the remaining functions. Shade, always.
One gentle de-tan clean-up, if there are at least three clear days before the wedding. It evens the top layer a little. Nothing stronger. A peel or bleach now is a real risk with no time to recover.
Match the base to the neck, not the face. A face lighter than the neck is what looks wrong in photographs, not the tan itself. Blend down the neck and onto the chest. Cover the arms if the line is sharp. Tell her in advance so she carries the right product.
Bleach on the face or arms. It does not remove tan. It irritates skin, and irritated skin looks darker and reacts under makeup. Hard scrubbing the neck. This is how a line becomes a patch. Booking three de-tan sittings in three days. Skin does not renew faster because you paid more.
Moisturise heavily, starting tonight. Sunscreen for every remaining function, and stay in shade. Tell your artist today so she matches to the neck.
No. A tan fades as skin renews, which takes about four weeks. In three days you can moisturise, prevent it getting worse, and have your makeup matched to your neck.
No. Bleach does not remove a tan and can leave skin irritated, which looks worse under makeup and reacts more.