I would say the main difference between Democrat and Socialist is that Socialists think more things should be run by government to benefit all people. However, Socialist is a very broad term. For instance there is the Bernie Sanders Socialism which is patterned after the Scandinavian countries. Then there is the Socialism being sold by the Party for Socialism and Liberation. They believe that the Revolution needs to be promoted actively. They broke off from their antecedent party the the WWP a decade ago primarily because they felt the WWP was not being activist enough. The WWP was a Soviet/Communist oriented party. They believed that the USSR did the right thing invading Hungary in the 1950s, that the Chinese Communists did the right thing violently putting down the Democracy movement in Tienanmen Square, and they supported the North Koreans. Here are some links to help you differentiate the flavors of Socialism.
https://en.wikipedia.org/wiki/Types_of_socialism [This article details more than a dozen varieties of socialism including Religious Socialism and Libertarian Socialism.]
https://en.wikipedia.org/wiki/Party_for_Socialism_and_Liberation [This party invades other parties like “Green” parties and attempts to take them over.]
https://en.wikipedia.org/wiki/Nordic_model [at Google, entering Socialism Scandinavian gives a number of sites]
Even if she knew the difference Hillary could not explain the difference very well in a 2 minute sound bite. Nor could anyone else. Now that you have read the links, how would you answer the question in 2 minutes?
There is no difference, government controls everything; about the only difference is the word used to describe it.
Easy. There is no difference.