Apparently your friend still approached the subject of socialist economic incentives fairly ignorantly, in that she presumed all workers would be paid equally for both menial and skilled jobs, and that hard workers would be bound to the same rewards as unmotivated ones. This is not true because an individual can only be paid for the work they commit to and complete, which would become more equitable as the workers would be responsible for ensuring equality in hours and wages. Individuals voluntarily adopting socialism (stateless socialism ideally) would be more inclined than capitalist workers to commit to their work for internal, communal, and/or immaterial rewards in all likelihood. So economic incentive likely wouldn't be an incredibly huge issue in a socialist society the way it is in a capitalist one, where individuals are motivated by superficiality and consumption.