I have a bidder who claims to put the wrong amount in and won the auction and now she does not want to pay.

First, put this bidder on your blocked bidder list.

Next, decide if you want to offer to send the bidder a request to cancel transaction.

http://pages.ebay.com/help/sell/cancel-transaction-process.html

Or if you want to file the Unpaid Item dispute:

http://pages.ebay.com/help/sell/unpaid-items.html

It's up to you, but I would file the Unpaid Item. Remember if the the buyer pays they can leave feedback. For the request to cancel the transaction the buyer can decline and you won't get your fees back. The buyer can also leave feedback.

Sunny "There cannot be a crisis next week. My schedule is already full." Henry A. Kissinger

The buyer had two ways to get out of the bid, one valid and the other invalid.

The valid way was to ask YOU to cancel her bid before the listing ended.

The invalid was would have been to use the Bid Retraction option within an HOUR of making the bid.

And then she waited a FULL day after the listing ended to tell you their sad story.

Not much sympathy here for this bidder. When a full 4 days have passed from end of the listing, file the Unpaid Item dispute. If she pays, ship when Paypal says to. If she doesn't pay within another 4 days, close the UPI with the reason the buyer didn't pay.

You'll get your Final Value Fee credited back on your eBay bill. The buyer will not be able to pay or leave feedback. She will get a UPI strike. If she gets multiple UPI strikes, many sellers will automatically block her from bidding for a full year.