You can't mark the limewire.props file read-only because LW saves it's settings on exit .
Preventing chatting in LW is impossible ...
Unless you compile your own version with a master password for the settings .

BTW : Be happy she is chatting on LW instead of on some IRC server .
Atleast on LW they can't swap porn (that easily) like Pokemon cards .
I used to be one of those porn swappers at DALnet and such .
Even had my own leech server .

I had to buy a extra HD after 3 weeks .