Let’s call her Slinky Sue. Floating, rather than walking, is how she gets about. She has never had to run for a bus (taxis always stop for her), but she has been known, in family games of Frisbee or tag, to totter a few yards in her high heels, in an appealingly helpless way, only to collapse giggling into the nearest pair of strong male arms.

She’s a bit of an airhead but so warm-hearted that men of all ages, from 18 months to 80, adore her. Slinky is warm and affectionate towards her own sex too yet, somehow, most women find her exasperating.

If she stays the weekend, you won’t see her before noon. A bonus, perhaps, the fewer full-Englishes you have to cook the better. But she commits the crime of wafting (when not floating, she wafts) into your kitchen with her face immaculately made up and her hair beautifully coiffed, wearing tight suede trousers and a pale pink cashmere sweater while you are in a fat-spattered apron, your face is red and there are beads of sweat on your brow.

“Can I do anything to help?” Slinky inquires. “Peel the potatoes? Make the mayonnaise?” What! In that outfit? She could have peeled the potatoes if she had appeared an hour earlier but, actually, you’ve just put them on to boil. As for mayonnaise, you don’t want her to know that you are planning on Hellmann’s disguised with a crushed garlic clove.

So you hand her the Sunday papers to keep her occupied till the rest of the family returns from football in the park. Then she’ll tell the winners how clever they are, and the losers how unlucky they were, and transform herself into an alluring barmaid, opening cans of lager or dispensing Bloody Marys. You’re still in the kitchen because you’ve been making said Bloody Marys.

There is a touch of the geisha about Slinky. At meals she becomes a submissive handmaid, leaning over, her shining curtain of blonde hair just brushing each man’s cheek, as she fills glasses and removes plates.

You must admit she’s a really useful waitress and she scores points by enslaving your stroppy three-year-old. She does it by engaging him in a gentle flirtation as if he were an adult.

There’s no need to be jealous of Slinky. She has no designs on the men in your life. She is simply doing what she does best: using her own assets and talents to make others happy — and surely we all aspire to do that in our different ways? So enjoy her company and, if you like, study her technique by watching carefully.

And don’t be goaded, as a friend of mine once was, to lean across the dinner table and hiss: “For God’s sake, stop being so pliant and sexy.”

Do you have a tricky family member you would like some advice on? E-mail Jane at body&soul@thetimes.co.uk. She cannot enter into private communication with readers. For more about Jane visit www.goodgranny.com.

NEXT WEEK: The Jolly Uncle