The woman's fiancé had proposed, but elation quickly turned to disappointment when the ring wasn't to her taste and was, she thought, a bit mean. He earns close to a six-figure salary, apparently, and the ring cost a meagre £1,300. Sterling.
"The first word that entered my head was 'small'," she wrote. She just didn't love it - but she didn't want to offend her beloved.
Those commenting were quick to warn her to "prepare to be flamed and called grabby, to be honest", but that turned out to be the least of it. People hoped her husband would leave her; she was accused of being the very worst kind of scumbag.
Out of all the bat-sh*t posts on Mumsnet, this one captured the imagination of the internet and even the mainstream media, and soon it had spread worldwide. Everyone had a view on whether or not she was being a spoilt brat. Opinions had been what she was looking for, just maybe not on such a grand scale.
"We're opting more for cheaper, coloured stones"
The subject line for the discussion thread was 'AIBU to be disappointed with my engagement ring'.
Now Mumsnet is known to be the place where acronyms go to die; they speak almost entirely in an impenetrable language of capitalised nonsense - from 'DH' (for Darling Husband), to FWIW (For What It's Worth) and LTB (Leave the Bastard). But this particular acronym - AIBU - probably sums up the raison d'être of Mumsnet and is the slogan of modern women everywhere: 'Am I Being Unreasonable?'.
Certainly, it's something I ask myself on a daily basis. But was she? It's well-known that all sense goes out the window when it comes to weddings - the threshold for reasonable behaviour rises considerably. Especially for the bride. And it is only right that the free pass for crazy should start at the moment of engagement.
So, I'm inclined to give the poor woman a break. Yes, if she's breaking down her betrothed's annual income to check if he's skimping on the ring, she might be a nightmare. But she also mentioned that she didn't like the colour of the gold, the setting and the "relatively chunky shoulders".
I'm fortunate enough not to know what the latter means, but it sounds sad. Anyway, the woman's dilemma seemed almost quaint. The idea that a man should spent two months' salary on a ring is the result of a ludicrously successful marketing campaign by DeBeers in the 1980s But that was a long time ago. Compared with 10 years ago, we're now spending 20pc less on engagement rings - in a recent survey, 50pc of people said they spent less than three weeks' wages.
Millennials have been blamed for murdering many industries with our mad spending habits: golf, movies, napkins, but one that looks to be particularly suffering is diamonds. We're spending more in the region of €500 on engagement rings and opting more for cheaper, coloured stones.
"No one wants to raise eyebrows with a huge rock on their finger gleaming for the world to see when there's no open bar"
Part of the reason is our bloody-minded insistence on being "unique" and "different" Diamonds just aren't cutting it (sorry) in those stakes. Celebrities from Kate Middleton to Halle Berry and Eva Longoria have put coloured stones centre-stage on their ring fingers.
But the biggest thorn in the side of the diamond industry is its ethics. We pesky millennials often don't want to contribute to a market which has been, and continues to be, the cause of so much conflict and violence. With that in mind, many of us don't want to create new demand for mining and so - like Scarlett Johansson and Natalie Portman - we prefer to go vintage.
It's easier to sleep at night with a dead-lady ring on your finger. And second-hand means more money for tiny cones of fish and chips at the wedding reception.
People in their 20s and 30s now just have different priorities when it comes to spending and weddings. If we haven't spent all our money on avocados and rent by the time it comes to settling down, we're more likely to want to put an extra grand towards the wedding itself or an Instragrammable honeymoon. No one wants to raise eyebrows with a huge rock on their finger gleaming for the world to see when there's no open bar. It's a recipe for wedding-guest resentment.
Of course, that's if we decide to settle down at all, which fewer and fewer of us are choosing to do. For those of us who take the plunge, the traditional trappings of weddings, with their backwards values like "giving away" the bride, promising to obey, and yes, engagement rings, are falling by the wayside as couples tend to want to start their married life in a more egalitarian way.
"Me, I feel for the ill-fortuned Mumsnet lady"
Anyway, the idea that we should sit around waiting to be presented with one and be thrilled with whatever we get is a bit galling. AIBU? Most men I know wouldn't even wear a pair of runners that their girlfriend bought for them without consultation.
Me, I feel for the ill-fortuned Mumsnet lady. It's like when your child comes home from nursery with yet another hideous finger painting - but you have to put it up on display for every day for the rest of your life. In the hall. Where it's the first thing anyone will see.
Most right-minded people will put it on the fridge for a week before slipping it silently into the recycling, or a special portfolio marked 'Felix', if you're that way inclined. It doesn't mean you're a bad person or that you don't love your child. The same should go for engagement rings.
Having said all that, if my future spouse is reading this: please, please don't make me choose - and make it cheap.
You see, I'm crippled by those other millennial afflictions: chronic indecision and irresponsibility. Dead-lady tat is fine by me.