"They've been away for a month-long honeymoon and asked if I'd like to flat-sit. I jumped at the chance because it's lovely there and it's much closer to where I work.
"I didn't eat their food. I didn't drink their wine. I fired up the computer once to complete a learning module."
The woman tidied the place and even left a thank you note.
"I cleaned before I left and changed their sheets for them. I left milk and fresh bread and a note saying thanks!" she said.
"This morning I got a message to say 'thanks for looking after the place. All right if we ask for a donation to cover a few bills? £300 ($580) okay?'
"I don't think if you ask someone to house sit you get them to sub your bills. Do you?!"
The woman said her partner had "half agreed to give them a 'token' amount when he was drunk with them at a pub quiz night" but that £300 was far from a token gesture.
Unsurprisingly, the couple's request for a "donation" has been savaged online.
One commenter wrote, "They sound deluded!" while another branded them "cheap b******s".
One asked, "are they taking this piss...?" and another posted, "What the hell?! They want to charge you for doing them a favour?"
Another wrote: "Why are you friends with such vulgar people? This is beyond bad manners."
Several posters suggested the woman should send her friends a bill for the same amount to cover her "house-sitting services", or to laugh the request off as a late April Fool's joke.