No - at best they might give a gram or two grace, but even something 10 grams over will be charged at the next price bracket.

Also, I'm assuming you mean there's 8 days of the auciton left? Unfortunately, it's very unlikely that an order of eBay satchels will arrive in that time. If the price doesn't stand a good chance of making up for the postage shortfall, she might want to consider cancelling the bids, ending the item and relisting with the correct postage cost.