Can payment type be changed after order is final?

I had a customer choose to pay with check/money order (to be mailed), then after the order was confirmed, decided she would rather pay with a credit card. Is there any way to back up and allow this, or do I have to delete the original order and have her re-submit it?

No, you can't edit an order once it's placed.
But you can process the credit card payment over the phone and add comments in the comments section of the order stating that the order was paid by CC along with quoting the authcode when you update the order's status.

Or, you could delete the order and she can resubmit one, and she can pay directly online ... assuming you're using a live gateway for your site's processing.

Thanks for the reply! Good to know!