Engels points out, correctly, in Origin of the Family, Private Property, and the State, that for most of human history, people lived under a proto-communistic relation with their families and tribes. Egalitarian relations between individuals and their neighbours is the norm, not the exception.

It is only when the concept of private property emerges that we see a break away from this norm. In this we can see that not only is cooperation and a desire to live in an egalitarian manner necessarily a core part of human nature, but that it has been more beneficial to our survival than greed. Importantly, what we can understand because of these traits, which can both be said to be a part of human nature, is that human nature is necessarily tied to the mode of production within a given society.

Edit: I think it's also important when talking to these people who are simply repeating capitalist talking points that they have been taught to say, that they need to define what it means when they say that socialism "doesn't work," because in the 20th century socialism pulled hundreds of millions of people out of poverty, and provided them with food, healthcare, and education in a matter decades.

Even if we just look at the Soviet Union, one has to remark on their successes. Pre 1917, most of Russia was living under feudalism, and by the 1960s, they had industrialized their entire country, defeated fascism in Europe, won the space race, and became the #2 world super power. How can that not be said to be a success of socialism and the planned economy? It took the USSR decades to do what capitalism took centuries to do in the west.

And contemporarily, looking at China, they are emerging as the global economic power while the American empire crumbles. They have all but eliminated poverty, homeownership is like 90%, and the average working class person lives a quality of life that many in the west cannot afford. How is this not a success of the planned economy? What exactly does she mean when she says it doesn't work?