The whole relationship that develops between Ofelia and Mercedes is very sweet. At times it seems to turn into a full blown mother/daughter relationship, considering the fact Ofelia's own mother is too weak from her pregnancy to really be there for her daughter. Mercedes is really the only one throughout the movie who is consistently kind to Ofelia and goes Mama Bear on Vidal:
And it is said that the Princess returned to her father's kingdom. That she reigned there with justice and a kind heart for many centuries. That she was loved by her people. And that she left behind small traces of her time on Earth, visible only to those who know where to look.
Mercedes humming the same song from before as she holds a dying Ofelia in her arms.
At the end, when the faun congratulates Ofelia for passing the final test. The sheer warmth in his voice shows he really wasn't half the jerk he made himself out to be before. He really did have Ofelia's best interest at heart the whole time, no matter what he had said up to that point.
Even earlier, despite being more concerned with Ofelia completing her tasks (Ofelia was a little behind because of her worrying over her mother's hemorrhaging from earlier), he still arrives with the mandrake root to help her out.
Later on, when the faun forgiven Ofelia for disobeying, and gives her a second chance. The embrace is even more heartwarming considering Carmen's death.