The "You are proceeding to an insecure website - do you want to proceed?" sounds like the default popup window that web browsers give you when moving from an encrypted (https) to unencrypted (http) page. As such, it sounds like it would appear after the transaction was complete and the user was being forwarded to some kind of "thanks for buying" page.
What was she supposed to get in return for paying? Can you tell us the company or software or is that not allowed?