Jesus said to her, “Mary.” She turned towards him and cried out in Aramaic, “Rabboni!” (which means Teacher).
Jesus only utters one word, her name, but it is enough for her to immediately recognize Him. When the Good Shepherd calls His sheep, they shall know His voice (John 10:3-4). Note the similarity to (Matt 14:25-27).
John 10:3-4 The watchman opens the gate for him, and the sheep listen to his voice. He calls his own sheep by name and leads them out. When he has brought out all his own, he goes on ahead of them, and his sheep follow him because they know his voice.
Matthew 14:25-27 During the fourth watch of the night Jesus went out to them, walking on the lake. When the disciples saw him walking on the lake, they were terrified. “It’s a ghost,” they said, and cried out in fear. But Jesus immediately said to them: “Take courage! It is I. Don’t be afraid.”
She had apparently turned away from the “gardener” to look again at the angels, but upon recognizing His voice, she whips around to face Jesus and declares, “Rabboni!” Now Rabbi, meaning ‘teacher,’ was a common form of address for a teacher leading disciples, but Rabboni was an even more honorable title, rarely given to men, but usually used only in addressing God in prayer. John’s interpretation of the word as “Teacher” shows us that Mary did not understand Jesus to be deity, but that she was using the term as “great teacher” or “highly honored teacher.” Her understanding of the Person of Jesus still had a ways to go.