Why not just use your host's FTP and download all to a folder on your computer when done? For a database backup, there are numerous WP plugins to do this and save to your computer (I'm short on time, so just do a search for backup plugins

).
When you are ready to upload to her site, make sure you do a 'find and replace' in the pertinent files and change URLs to what they should be from what they are in your subfolder.
HTH a bit,