I would start with "learn c the hard way" and when she is confortable, go for c++. c++ has some idiosyncrasies as a high level language that are better understood from a c point of view.

As a casual c programmer, I've found this "c to c++" tutorial very useful:

http://www.4p8.com/eric.brasseur/cppcen.html

It now appears to be offline, so here is the cached version:

http://webcache.googleusercontent.com/search?q=cache:http://...