Because she is probably gonna want to get a tone of work done...so it look likes a new build garden. Fake grass, grey fence panels, decking.
Mature gardens are hard work, old houses are hard work - they are wonky, rough around the edges and never standard measurements (for curtains etc).
Old houses are everything she is not, they need investment, commitment, time, effort and have tonnes of character.
It really confused me why they didn't go for a new build? A pop up ready made beige house is exactly her thing. I don't even think there would be that much of a price difference..so she could boast just as much with a new build.