I have experimented extensively with this issue. It is related to the recipitants email app, but in previous versions of Mail could be made successful by clicking on Format/Make Plain Text prior to sending. In Mail in Lion, ML, and now Mavericks this change does not stick, and the message utlimately gets sent in Rich Text/HTML which is why the MS apps have problems.
The Make Plain Text strangely enough endures if you add a Signature following the attachments that is EMPTY but composed as text only plain text. This 'tricks" Mail and OSX to not change it back. I cooresponded with Apple engineering about this, and they say the use of Rich Text is necessary and helpful with Exchange Accounts. But this does not help the many who are not in Exchange Account Situations.
The use of Attachment Tamer in general can help this, but I don't use it, and it is not clear to me how it would work when invoking Mail sending from within Aperture (or iPhoto which suffers the same issue).
I have not experimented with this issue in iOS devices, and was not aware of it being a problem there. But it may be the same issue.
A similar issue can be found not involving Apple devices -- see:
http://forums.androidcentral.com/samsung-galaxy-s4/364477-cant-receive-email-att achments-when-sent-using-rtf.html
Also note the instructions MS has for formats to send messages (not that this is helpful to a message you receive):
http://office.microsoft.com/en-us/outlook-help/change-the-message-format-to-html -rich-text-or-plain-text-HP001232996.aspx
Apparently Exchange networks complcate the design of email formats, and I believe there are ways to actually find the supposedly embedded attachments, but I am not currectly using any PCs to experiment with. If you you would, take one of the messages from your wife that you PC find problematic, and use the command to send again. Observe whether the newly composed messages show the attachment.
Ernie