It depends though - a lot of people have MBP's and they all look alike, especially when closed and turned off. She could have taken it in error. Now, the fact

It depends though - a lot of people have MBP's and they all look alike, especially when closed and turned off. She could have taken it in error. Now, the fact that she didn't leave her own MBP behind is a strong indicator that she didn't have one (or at least didn't have it with her), and that she intentionally took someone elses laptop.