I am not my daughter's best friend, nor is she mine. Our relationship is much more important, and fundamental, than that. Sarah is my one and only daughter and I'm the only mother she will ever have.
US family psychologist Dr Stephen Poulter nailed it when he said mothers who try to act like their child's best friend leave that child motherless. I couldn't agree more. He went further, saying that best friend mums could be scarring their child for life.
A mum who thinks she's her daughter's best friend is deluding herself. Quite simply, that's not a mother's job. A child needs a parent, not another friend.
Most of all, best friend mums want to be liked. But motherhood isn't a popularity contest. As your children grow up, you have to place boundaries, be boring, say 'No'.
Best friends come and go — but, like it or not, Sarah's kind of stuck with me. Best friends compete — we don't: how daft would that be?
Best friends even share a spark of envy or jealousy — I can't think of anything more ridiculous between mother and daughter. And, unlike most best friends, our inevitable rows are always forgiven and forgotten.
In short, best friends is not the best thing to be.
Dr Poulter referred to a few US celebrity families to illustrate his point, but made no reference to our royals. Like many other mums, I cringed at Fergie's ill-judged 'joke' about going out 'on the pull' with her teenaged daughters, Bea and Eugenie. The nearest my Sarah and I ever got to that was a session on the exercise machines down at the gym and even then she left me standing.
Anyway, it would never work: as well as a 30-year age gap, I'd be the dumpy brunette to her willowy blonde. Imagine the cries of 'I don't fancy your's much'.
The best friend pattern may fit better with, say, a 17-year age difference rather than a true generation gap but, even then, it can come across as sad and a bit desperate.
Mums and daughters with the same hairdo and a shared wardrobe, who go out clubbing together, has the whiff of competition about it, an edge of sibling rivalry. Altogether in bad taste.
The lifelong mutual support of real love and caring, even long distance, is something quite different. It goes deeper than friendship. Just don't expect your daughter to get it until she has a child of her own.
Best friends rarely get the chance to be in at the beginning of a life story. Mums, naturally enough, get to do that by definition — from the birth bonding, to their baby's first shaky steps, to the day they stride out the door towards an independent life.
My toddler daughter's first inaccurate but determined sentence, as she grabbed the feeding spoon from my hand, was "My do it myself". It was a sign of things to come. Years later, there was no need to count the candles on the birthday cake. I had proof positive she was tottering on the brink of her teenage years. She went through a phase of fixing her hair in the mirror before she'd answer the phone.
Fast forward again to Upper Sixth when Sarah wanted me, and only me, to travel to Scotland with her for interview to medical school.
We'd spent months together organising vital work experience, honing an appliction and swotting up on long lists of questions that just might come up. She even asked my opinion on what to wear (definitely a first).
Then, at the last minute, she asked me to stay behind in the hotel room as she made her way to the hospital alone. She was all adviced-out. I'd only make her more nervous. So there I sat trying to concentrate on Loose Women on the telly while she succeeded without me.
It's one of the hard rules of motherhood: be there when you're wanted and know when to back off when you're not. I know she'll always turn to me if she's ever in need and that's good enough. I might give her an earful but I'm always in her corner.
I love that she cooks like me and that we have similar tastes in many things. I love shopping with her — even on her first visit, aged 15, to the big Topshop in London's Oxford Street when I trailed around after her like a weary clothes horse. I even love puffing along behind her on one of her power walks. She has taught me how to use eBay and has long ago given up on trying to teach me how to text.
I've looked askance at any boyfriend she might bring home and have to remind myself that, unlikely as it might seem at first glance, some mother loves him too. It's great when we have a late night conversation and she chats away freely before catching herself on, realising I'm her mum and that's way too much information.
I've listened in awe when she tells me of witnessing her first emergency Caesarian or taking part in her first cadaver disection and thought 'Already she's done so much more than me'.
I'll help her save for a backpacking trip to Thailand and then scour the news anxiously for any accidents, murders, mayhem and natural disasters that may be happening over there. What's wrong with a fortnight in Ballycastle, for goodness sake?
I look forward to her coming home in the long holidays. The house is so much tidier and duller without her, less colourful and, literally, less fragrant.
I loved my daughter before she was born. Like any other mother, I'd die for her. Pushed to the edge, I'd kill for her. A best friend might let you borrow their last pair of tights. No contest.