I recently sold something on eBay. The recipient hasn't paid yet. What should I do?

It's been almost 48 hours since the auction ended. After the first 12 or so hours, I sent an invoice as a reminder. I've just sent an e-mail to the buyer reminding them to pay. How long should I wait to take further action...and what action should I take? I have a perfect feedback rating and don't want to give negative feedback to her for fear that she'll retaliate with negative feedback for me.