The authorization information panel makes it look as if it should be possible, but I can't see how.
The online help says to see the 'Getting Started' book, which doesn't seem to address the issue.
You could try opening one of your wife's books and see if it prompts you for a second id/password.
I don't know how important it is for your wife and you to have separate AdobeIDs.
If you share an ID, then you can share the books as well on your different eReader devices;
you can use an AdobeID on up to 6 devices (computers, tablets and ereaders).
That also gets simplifies authorization on the computer.
It has worked very well for my wife and me.
If you've already gots lots of DRM books locked to each of the two accounts that isn't feasible
(unless you DRM strip all the books from one account before you abandon it).