You have to set the rules. I would send her email with title “FINAL NOTICE”.
Then I would try to be business like. Something like "As I have not received any further payments, and the due date for final payment (29th November) has passed, I am assuming you are no longer interested in this doll. If you still wish to purchase her, please pay another installment of $X (at least half of what is still owing) within 7 days, and the final payment by x December. Failure to do so makes our agreement void ". Or if you do not want to mess around with her anymore, just say that if final payment is not received within 7 days, you consider the transaction cancelled.
I always relent if somebody comes back with sob story; that is another reason I stay away from customs But unless you set your rules then it can get messy.