I usually order Diet Coke or coffee when I know I'm going to be driving. Woman can't absorb as much alcohol and still be sober enough to drive as can men (due to size differences, I suppose), so it is not uncommon to see women drivers not drinking at events where male drivers feel free to have 2 or 3 drinks. Unfortunately, men seem to be greater risk-takers when it comes to booze and driving. I'm not saying this lady did not drink (how would I know?), but I am saying that it is not at all unreasonable to believe that she did not.