When a wedding guest gave the bride and groom a £100 gift, she thought it would be gratefully received.
So she was understandably appalled to receive an email from the bride - a former colleague - suggesting she "adjust" the size of her cheque.
And, when she turned to internet forum Mumsnet for advice on how to respond, she was inundated with more than 1,000 replies from aghast users.
The bride and groom had requested cash gifts and she sent them a £100 cheque, which she considered "pretty decent", the woman said.
The couple duly emailed her after their honeymoon, saying how pleased they had been to see everyone.
But the email continued: "We were surprised that your contribution didn't seem to match the warmth of your good wishes on our big day. In view of your own position, if you wanted to send any adjustment it would be thankfully received."
The woman, who described herself as retired, said she had received an inheritance recently, and wondered if the couple had been suggesting it meant she should be more generous. She told Mumsnet: "For someone who's not easily shocked I confess I'm utterly gobsmacked by this.
"Please, anyone, what do I do now? I've never come across anything like this before and still can't quite believe they've done it."
Appalled Mumsnet users replied in their hundreds to suggest she cancel her cheque and "name and shame" the ungrateful couple.
Others suggested she should ask them to return the £100 and replace it with an etiquette guide to good manners. And one said simply: "Watch this marriage like a hawk... the moment they start divorce proceedings then you must ask for a refund."
The guest said her cheque had been cashed but the couple had not said thank you. She added: "I certainly won't be sending any more, even as a joke; I wish I'd given a tatty fiver, then she really might have had something to moan about.
"All this was ever intended to be was a nice gift and she's turned it into something unpleasant which is a crying shame.
"I really didn't see this coming and now it has I'm not going to concern myself over what people think of her; she chose her own actions and she'll have to live with them."
The guest, who did not want to identify the bride and groom, said later: "I've just replied to her email with one sentence: 'I assume this was some sort of mistake?'"