So, does she want these cars for daily driving, or for more sinister activities?
For pure performance, go G35 without question.
If this is a car thats going to be used all year long, the TL may be a bit better (unless of course the G35 is AWD).
Looks, well thats all on opinion so I can't make a call on that one.
How about warranties? I assume that these aren't certified pre-owned cars due to the mileage, but what about powertrain warranties? Do either of these have powertrain warranties still in effect?
On a side note, it'* amazing what you get for $20k these days.....