@onlychildhamster I am just unsure how it translates in cheaper areas
I don't think it does, if I'm honest. It's a very London thing. It's not even a thing where I am, and people struggle getting on the property ladder here, too. Generally here, if you can't afford a central property, you live further out and drive in. Public transport is okay around the centre but woeful further out.
The flat you've linked to is a modern auction - that's the starting price, so it'll likely go for a lot more than that, but the buyer also has to pay the reservation fees - £6k or so in that case - and it's legally binding once you've made an offer, so you can't pull out like you can in a "normal" sale. There's also no mention of lease length, which could be fine, but might suggest that it's not got long left... If it's over 80 years, extending it will likely be less than £10k, but if it's got less than that, marriage value comes into play and it could cost a fortune to extend.
I really think she'd be better to rent somewhere before she buys if she wants to move areas, so she can make sure she likes where she ends up, and she can see where the cheaper areas are.
I've lived in five places in the Midlands and renting a room isn't really a thing here, unless it's a student house. There wasn't even much of it in Birmingham when I was a student - it was houses with other students, rather than lodging with a landlord.
There might be other places where that still happens but I think it's a really London-centric thing, similar to people being willing to provide care/cleaning/shopping etc in exchange for cheaper rent.
If she knows people in London and wants that type of set-up, is there no way she can stay? Even if she moved a bit further out, or downsized a fair bit, it'd probably be more similar to what she's used to then moving somewhere else entirely...