You are not required to use any service other than those you list.
Send the bidder a polite note saying you are sorry that she can't afford the total cost of her purchase, but your prices are firm, including those on shipping.
Don't explain why. She doesn't care. In fact, there is a good chance she actively wants you to send without tracking so that she can start a false Item Not Received Dispute.
If you don't get payment, start an Unpaid Item Dispute. You can do this as soon as four days after the purchase.
Had a problem with your attitude, is why. Felt you was - what's the word?-- Badger