If she arrives at 7pm why not contact the airline to see if she can leave the same day. Just depends on flight avaliability or maybe standby.
Terminal 6 wouldn't be my selection for overnight since everything closes. My suggestion would be Terminal 4, it is an international terminal and the flights are always leaving - atleast when she waks up middile of the night she can grab some coffee or water etc...
Good luck
If she arrives at 7pm why