Centaurus
If your student has a PC at home, then there is a superb little program, totally free, at
http://www.visi.com/~mim/nav/
This helps develop situational awareness and, as an added bonus, covers the VOR, RMI, and HSI. Your student can set up her own scenario's and 'fly' them at home, watching both the position of the aeroplane and the ADFs (of which there are two; the two NDBs can be repositioned at will).
It really is a gem, and should be on every instrument student's PC.
I would be interested to hear if you think it might help.