Lots of people don't have a clue about what it means to be self-employed, or use the services of a self-employed person.
I am self-employed. I have been working at home since well before the pandemic. It's not MLM. It's not selling "glittery shit". I have come across so many attitudes that it's not a proper job, that it's just playing, a hobby, that I must be fiddling tax. 
This cleaner is SELF-EMPLOYED. That means that she doesn't get many of the benefits which come with employment like sick pay or holiday pay. But it also means she gets the flexibility to take what jobs she wants and sets her own rate, and gets to choose how she gets paid.
She wants cash and that's her choice. If you don't want to accommodate her choice, then she can choose not to work for you. What she does after you leave a pile of £10 notes on the table in terms of tax is NOT your responsibility as a client any more than it is your responsibility to check up on the hairdresser, car wash guys, plumber or window cleaner.
People who don't understand what self-employment is, and how it works, really do spout off a whole lot of nonsense about employees, employers and "duties".