Mine doesn't go as quick when Audrey is a passenger

I get the feeling it doesn't go as quick for Audrey either when I am a passenger.
Seriously though, 100kg can make a difference to the performance of your car. Maybe not really noticeable but a difference it
can make.
Take for example: the bunfights over the last 5 or 10 years between magazines over acceleration times. Some decided to test the usual 0-100km/h, quarter mile and such with a passenger and half full tank, while others (and manufacturers) chose to test with a near empty tank and just the driver. This often made a half second or so difference (down in the 5 or 6 second bracket for the 0-100km/h test) with a weight "penalty" or no more than 100kg.
In normal driving however, I reckon you would have to be very perceptive to notice the difference between having a passenger and not. It may well be you changing your driving style (as I know I do).
Anyone who can pick the difference between full and empty fuel tank in normal driving is either tremendously perceptive or kidding themselves (or their "normal driving" equates to track driving at/over the limit) IMO