They seem definately lower than what I've had out of it, and given the book speed for these things is 106mph (from memory), I'm suprised you couldnt get it to at least 110 indicated.
Is something up with your wifes car, or is it the older model with a 60bhp engine rather than the 70bhp or something?
I really see no reason to lie about hitting 90mph in 3rd, even though this is indicated I doubt it'd be out by more than 10% at the very most.