To load up the songs into the mini you can just plug it in.
You're second Ipod (mini) will hold the first 700-900 songs on the iTunes list unless the unwanted songs are unchecked in the box next to the song.
Be aware that once the mini has loaded songs from your iTunes library, it can not be loaded with songs from another computer.

Hope that helps.

You can also do like Ranj says and make another profile and have her load up her songs.