I haven't seen that particular issue, but add-ins can mess with the context menus, so it's possible she has one installed that has mucked up the existing copy and paste. You can try running IE in no add-ons mode
(that link is old but I think it's the same in IE8/Win7). If that works, you could also try selectively disabling whatever add-ins she has installed to try to isolate the bad one. A lot of users install toolbars and other dreck (sometimes unintentionally) and this is sometimes the result -- with context menu items to do everything from translating the text into other languages to blasting it to every social network under the sun, but not the mundane functionality you actually use/need.
I think it may be possible to control copy/paste in IE (and elsewhere) via Group Policies (IIRC) but it seems unlikely that would be the case here.
Of course another solution would be moving her to one of alternatives to IE -- I believe right-click copy/paste works fine in Chrome, FF, and Opera.