I don't have IE8 so I can't check this, but for now, if you know where IE8 History is stored you could exclude that file from being cleaned with CCleaners "Options\Exclude\Add File or Folder", or even Add Registry.
Just to make sure, have you checked that "Private Browsing" isn't enabled in your IE8? That would remove History on closing.
One of the guys on here using IE8 will hopefully be able to give you a solution.
As Dennis said, make sure your InPrivate Browsing is not enabled. If it is enabled, you will see ?InPrivate? in the address bar. Another thing you may want to check is that the option to delete browsing history on exit is not selected. To double check this, go to tools>Internet options and under the General tab there will be a section labeled ?Browsing History? which is where you can make sure ?delete browsing history on exit? is unchecked.
I have Internet Explorer 8 and I tested your case. Here is the result:
Depending on what exactly you mean by history, make sure the following items are unchecked:
Index.dat: Always leave it unchecked unless you have checked everything else.
History: Leave it unchecked if you wish to have the contents of your History pane intact. (History pane is the one that appears to the left of your browser window.) Internet Explorer 8 also searches History from Address Bar (which is cool; I wish Firefox could do this as good as IE.) Also leave it unchecked if you want the item below intact.
Recently Typed URLs: Leave it unchecked if you want to addresses typed in your Address Bar to be remembered. (I believe this is even more important that for your wife.) This list is accessed by pressing the drop-down button beside the address bar.