You should race her car at the track (full 1/4 mile).
Here's a video of a stock IS350 running 13.7.
And I also read where a guy was runnng mid 13s in winter conditions in his
IS350.
Here a slip of another stock IS 350 in 49 degree weather.
1/4 Mile ET: 13.420
1/4 Mile MPH: 103.120
1/8 Mile ET: 8.640
1/8 Mile MPH: 81.840
0-60 Foot ET: 1.980
Temperature F: 49.0
So they are pretty fast. But if your car was running at 100%, you would be beating her car by a couple lengths in a full 1/4 mile race. A good tune is all you need.