Can a player demand to see my folded cards because I showed my neighbour?

How to use this answer

A definitive win, loss, void or refund cannot be established from the question alone. Identify the operator, the exact market, the date and the relevant official result, then check the rules that applied to the bet.

Tournament rules are a useful reference, but a home game or cash game can have different house rules. Make the chip amounts, action sequence and card visibility clear before deciding a disputed hand.