I Won A Bid On EBay, Can't Contact the Seller?

[Nani]

I had finally found this shirt that I was in love with at topshop but it was out of stock so I went to eBay. I found a girl who was selling hers, bidded, and won. I live in the U.S., the seller lives in the U.K.
I click pay now but it says " Topshop Uk12 Scallop Trim Canary Yellow Crop Top BlouseQty:1GBP 7.50
Please change your address or contact the seller to request an exception by requesting total. "
I requested an exception by contacting the seller, haven't heard anything in 2 days. But she has alot of positive feedback. There's also another girl who's selling the same shirt, but the auction ends in an hour . I've talked to her and she says she does ship to the U.S. (also from U.K.)
Should I bid for this one and forget about the one I won? Or should I wait until I hear something from the seller of the auction I won?