Such a costly silly temper tantrum. Chances are that she didnt buy outright and is paying monthly, so technically the car is not hers. If this is the case its criminal damage. In addition the insurance will not pay out as its self inflicted.
I agree with the answers about a Thai citizen being allowed to enter Thailand. However some airports and airlines have uninformed check in agents who are real job worths. Be prepared for an arguement just in case and try and get some printed proof to take with you.