She should ask LH about the earlier flight. If she is there so early and her flight happens to be delayed, cancelled or oversold then they may jump at the chance to take her earlier. With such a long layover it shouldn't be too difficult to get the bag checked on to an earlier flight. She could even just ask for the bag to be checked to FRA so she can collect it and then try to get on an earlier flight and simply re-check it. Less chance of the bag going missing in the transit area too.
If she holds a normal ticket (i.e. she's not a staff traveller, which seems to not be the case if she booked through an agency) then the chances of them offering standby are slim to none. It will more than likely be a Yes or No answer as to whether she can go earlier or not.