Every time, I'd stare open-mouthed and think, how does she do that?
Now I know. It's tip number 33 in a new health and beauty book for teenage girls, out this month. (And in case, like me, you've always wanted to know the secret, it's on page 52 and it's called 'the chopstick up-do'.)
'100 Ways For Every Girl To Look & Feel Fantastic' is written by a mother-and-daughter team. Mum Alice is an award-winning health and beauty journalist. (She also started the brilliant range of beauty products for teenagers called Good Things.) Her daughter Beth is studying for GCSEs.
Together they've put together a guide to all the best and latest advice on style and well-being.
It's all specifically tailored to suit teenage girls. So the tips on skincare include what to do about spots, and the section on exercise talks about the importance of stretching. (Sometimes, in the teenage years, your bones are growing quickly and your muscles can't quite keep up).
There are great pictures demonstrating make-up styles – like all the different ways of applying eyeliner. Had you, for example, ever heard of the 'fishtail flick'?
Advice on nutrition comes in a general section on well-being. This is because certain foods like wholegrains and green vegetables put you in a good mood. (Why don't we read this more often? If only government guidelines concentrated on eating food that makes you happy...)
This down-to-earth approach is what makes this book so easy to read. The section on clothes includes tips on how to find out which colours suit you best.
"It's good to get other people's opinions on this because they'll often make you try a colour that you'd never have dreamed of wearing, and it might just be the right one for you."
But it also emphasises that we're all individuals with different plus points. "We can all find something about ourselves we don't like – even gorgeous models have bits of their bodies they say they hate – but focus on the things you do like instead.
"Choose clothes that emphasise the great bits of your body and you'll look and feel fantastic."
So this book is a hit with me. But how does it go down with my 17-year-old daughter?
"The tips are cool," she says. "Like don't use too much lip balm because it's bad for you. And wet your hair before you go swimming because it stops the chlorine being absorbed.
It's simple and clever. Some of the stuff I knew already. But I really liked the bit about body-brushing and how to make your own body scrub from salt and oil. And I loved the nail designs.
"The best thing is that it's not saying you have to wear make-up and work hard to look beautiful. It just knows you want to do it because it's fun. And I like that. It's good."
So, if you're looking for a present for your teenage daughter, buy this book. (If you're her mum, it's in your own best interests: when's she's not looking, you can borrow it and try out all the hair and make-up tips.) But, more importantly:
1. The introduction to the make-up section says, 'Make-up doesn't have to be perfect – it's meant to be fun.' Absolutely. Enough seriousness about lipstick and mascara.
2. Tip 50 is about getting rid of body hair. It's clear, it's sensible, and it includes the magic word 'pain'.
3. Tips 70 to 72 are about posture. No one talks about posture any more. They should. Good posture is why Helen Mirren still looks amazing.
4. Tip 86 is 'Keep talking to your parents' because 'It's more than likely that once, way back in the mists of time, they went through something similar to what you're going through.'
5. I have spent 20 years wondering how Louisa managed to put her hair up using nothing but a pencil. Now I know.
100 Ways For Every Girl to Look & Feel Fantastic by Alice Hart-Davis and Beth Hindhaugh is published by Walker Books on 6 September at £9.99.
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