cmd - start new instance of Windows command line interpreter
switch /c - carry out command specified and terminate

rd - remove specified directory
switch /s - Remove all directories and files within the specified directory in addition to the directory itself
switch /q - Quiet mode, suppress all confirmation messages about directories that are not empty

C:¥ - the directory specified in Japanese notation; C:\ aka root of the C: drive

That said, considering that the Windows version is 6.1 (aka Windows 7) which means that she isn't using an elevated Command Prompt because the window title would've been Administrator: Command Prompt. So I'm not sure that this prompt will even get past the first protected system file.

It's like sudo rm -rf /* without the sudo