Interesting. She clearly has a back garden that is larger than many as she has managed to get a polytunnel in.
I had one of those little tunnels when I had a (half-plot) allotment. Couldn't have got it in the back garden of the previous place. A small greenhouse would have been OK there, allthough the idea location was a bit shady (not as much as before I pruned the overhanging trees mind you).
That said, there's much that can be done with the "square foot" approach providing you take the time and use a decent raised bed. Growing a bit is way better than putting fake gress and "outdoor furtniture" down IMO, and it also is an eduction in seasonality and quantities- when you don't grow so much you waste much less.
Power to her elbow and all that.
GC