Neither do I. There's things like landlord insurance that might limit the number of occupiers. I reckon she'll be renting from someone she knows who has an existing tenant who has given notice. Which is why she's going on about moving in 6 months.
If someone wants to rent and they pass referencing the landlord won't care in general. She doesn't have him full time and it's her business to sort out arrangements for sleeping etc. She might not disclose there's another person stopping over a few nights a week.
Social housing is different, in that you would choose to disclose a dependent needing their own bedroom and they would be obliged to provide the 2nd bedroom...IF the child was there for x amount of nights.
Only thing generally stopping a landlord letting to more people than bedroom ratio is if there was a family of say 7 moving into a 3 bed and they were worried about undue wear and tear.
Landlord insurance aspect: it still generally comes down to the actual tenancy holders. X and y are on the tenancy agreement. Have they passed referencing? Good to go.
Coming from the past so apologies where this lands and if it's been covered
![Grimacing face :grimacing: 😬](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f62c.png)