How to disable 'immediate payment required when Buy it Now is used'.

[trulyspecialgoodies]

Buyer has bid on an item instead of using Buy it Now because I have the 'immediate payment required' option ticked. I told her if I cancelled her bid then the Buy it Now would be reinstated and she was happy for me to do this but I can't disable the 'immediate payment' requirement and she is unable to pay till Monday. Help!