My bad. In the first place, what I meant is that you can't give up copyright - you can't say "this work is in the public domain". (Or rather, you can, but there's nothing legally preventing you from saying a year later "I changed my mind".) See http://www.rosenlaw.com/lj16.htm
However, "inalienable" was incorrect - you can most definitely sell your copyright.
just to clarify because i think you sort of said you were wrong but i'm not entirely sure...
if i read 17 U.S. Code § 201 (d) clearly, it suggests you can transfer ownership of copyright in any normal legal way of executing a contract.
I think your confusion is around the idea of works falling into the public domain via expiry of copyright, and/or works that do not have an explicit declaration of rights ownership.
In this case it seems she was pretty clear about her transfer of ownership. I don't believe you can rescind that just as you prefer, at any time.
