While Maria is shopping, she notices a teenage girl slip a tube of lipstick in her purse and walk away. Maria thinks about it for a moment and decides that as a witness to a crime, she has an obligation to do something. What part of Professor Robert Sternberg's ethical reasoning model is Maria in at this stage?

She is in step number 6 of Stenberg's ethical reasoning model.

Explanation:

Robert Stenberg, Professor of Human Development at Cornell, developed a the ethical reasoning model in eight different steps. In number six, the person must decide how the ethical rules actually could be applied to a specific problem, and it usually comes with a solution. The problem is the girl taking the lipstick, and the solution is Mary's decision to act about it.