FINGERS, cool, lined, knuckles like walnuts, grab my wrist. "Argh!" I shriek, as she swings my hand down and away from the shelf as though I'm a one-armed bandit and we're in a Vegas gambling hall. She wouldn't look too out of place in a Vegas gambling hall, my new friend, (blue hat, red coat, lots of clinking gold) until she opens her mouth.

"Haud on!" "What?" "Don't touch it! It'll come down at 7.20pm." It's only 7.15pm.

We are in the supermarket at the reduced-price shelf and, despite her insistence, I cannot for a minute believe anything in 2011 runs to time. But no, after a trip along Bakery and back, there are the boys with the discount gun and there is the lady, perched on one young lad's shoulder, squawking instructions.

"You can take more aff than that." "I can't." "Tch". Without pause, without shame, our heroine grabs the price gun and begins administering her own economic justice. "You've got to show these boys how it's done."

My friend Janet introduced me to the joys of the bargain shelf a few weeks ago. You have to go at around 7.15pm when the yellow discount stickers begin to appear and be in the scrum by 7.20pm (I now know) for the best bargains. Janet, a thrifty soul with a healthy appetite and healthier imagination, comes up with marvellous soups and other foody concoctions but never seems to spend more than £8.87 on her weekly shop.

After months of prodding she whispered to me about the discount food shelf and the 7.15pm witching time. But this lady takes the cake. And the mildly bendy parsnips, the 10p double cream and a four-pack of chicken breasts that are pulsing slightly.

"Chicken?" The chicken sighs lightly inside the plastic wrap. "I'm vegetarian." She looks at me with suspicion. "I eat fish, though." She clicks a 25p label on some cod fillets and balance is restored. A mum with a wee one kicking his legs off the trolley gets 12 baby yoghurts in a bag: 69p. Another old lady gets a shepherd's pie meal: 12p. She doles it out like Robin Hood.

"Bargain Betty," the shopboy breathes with a dismissive shake of the head. I'd be less dimissive, were I him. A few more lessons from Bargain Betty on sticker prices and we'll bring the supermarket monopoly crashing down.