Don't know much about Jack Monroe, never heard of Allegra, and not sure what the "test" is?
But having looked at Allegra's wiki I'd say she's very upper middle class, verging on upper class?
But very much agree with @frozendaisy
It has not so much to do with money as the things she mentioned - interests, hobbies, skills, lifestyle.
I was walking through one of the stations in London with a piano recently, young guy in in high-vis and splattered trousers (paint, cement, not sure) was playing the most beautiful music on the piano. At first glance he looked stereotypically working class (manual job) but had clearly been classically trained in piano.
I guess where money comes into it is that you generally need money to have the time and means to pursue hobbies such as this - instruments and tuition are expensive, ditto for painting, skiing etc.
But in general, meh, I don't know.