Tell her they have 7 days to pay - to stop her worrying - then file a non-paying bidder alert as soon as you can and relist.
When you relist you can specify buyer requirements - such as no bids from people with less than a certsin % feedback or with less 25 feedbacks etc. That will help it go more smoothly next time.
It's a PITA but ebay is seriously going downhill. I have had this happen to me several times and on one occassion they did pay up in the end (they had lost their internet connection) so there is hope.
You can give second chance offers to losing bidders to speed things up if you wish (saves relisting and you can choose who you offer the item to)