You can go to your Seller Admin > Re-activate Expired Links to revive the download link she already got, or use Send Free Download Link to issue a brand-new link.
Her link may have been prematurely expired by antivirus or other security scanning software; for this reason, we recommend our default expiration setting allowing 5 attempts, certainly no fewer than 3 attempts at bare minimum.
Note that the download attempts setting can only be used to determine how quickly their link expires; it cannot be used to limit how many copies of your file the buyer can have, as explained in more detail here:
http://www.e-junkie.com/ej/faq.download-copies.htm