There are two ways.
1. restore her user account to your Mac, that way she can log on with her account and use it like she did her iMac
2. connect Time Machine, navigate to the latest backup, user folder, pictures and copy the iPhone Library to your desktop. Rename the library to "wife name iPhoto Libary" and copy it into your pictures folder inside your user folder. Now when you start iPhoto and go to the file menu you can switch to her library.