You hav to move the photos from Aperture to iPhoto to do this.
1. Using the Media Browser you can drag from the browser to the iPhoto Window - this yields the Aperture Previews
2. Export from Aperture to the Finder, import to iPhoto.
That said if you use Apple's Mail.app you can
A: Take advantage of the Stationery feature, which has more templates than iPhoto, more varied thatn iPhoto and others can be downloaded
B: It's a full mail application, with an outbox and so on
C: You can email from Aperture, and so avoid this loop into iPhoto.