Is she using Outlook? Outlook Professional 2010? I've found that with XP users sometimes had to drag an attachment to the desktop, and then open it from within Word. This was usually when the sender had attached a document saved on a Vista or Windows 7 machine (.docx). The older versions of Outlook and Word couldn't open them without a translator. But Outlook Professional seems able to handle everything. You can designate Word as the program for opening email. Again, whether word can open everything depends on which version of Word it is.

Also, people would try to open attached files from the preview pane, and that didn't work... had to actually open the email first.