They likely have a clause allowing them to cancel her contract purely for convenience and even if they didn't, a lawsuit would cost > $100,000 and take several years. A better tactic is to encourage your fans to get their tickets refunded and chargeback if necessary.
Mass chargebacks are awesome. They don't just return the money, they pay a fee to the credit card, so they can actually end up with less than they started if enough people chargeback.
They likely have a clause allowing them to cancel her contract purely for convenience and even if they didn't, a lawsuit would cost > $100,000 and take several years. A better tactic is to encourage your fans to get their tickets refunded and chargeback if necessary.
Mass chargebacks are awesome. They don't just return the money, they pay a fee to the credit card, so they can actually end up with less than they started if enough people chargeback.