It sure looks like your friend's ISP email setup (read: mail servers and filters) causes what she sees, perhaps in conjunction with her email program.
One last thing you could do on your end is to check the encoding you use for attachments to your outgoing email (the body text encoding itself is set automatically). For Windows recipients attachment encoding is best set to " Windows(MIME/Base64) ". In Mail you'll find that under the Edit>Attachments menu as 'Always Send Windows-Friendly Attachments'. This will not likely fix your friend's current problem, but ensures that you've done all you can on your end.
