>>568
"Mom, Dad, meet my girlfriend. She's ten years older than me."
or some variation of that...
Alternatively, you could just not tell them. They would be faced with the prospect of rudely asking her age, and when they do, your older and wiser girlfriend might be able to handle the situation better. If wisdom is actually a direct function of age.

>>570
Is wisdom a function of age, and if so, what is the function?