360share is a site which lets you search P2P (Peer 2 Peer) networks (Edonkey, Imesh etc) all of which are actually free and you can download their clients for nothing, however it looks like 360 lets you search them all from one place.
In itself none of these file sharing systems are illegal, however they are used mostly for downloading a sharing copyrighted Music, Movies etc and that is very illegal.
Personally i would steer clear of it and tell your daughter to look into bittorent, however thats also used for illegal file sharing, it's just faster and free!
Hope this helps.
Jen