The two Marys stand in history as the most blessed of women: one Mary gave birth to the Son of God, the other, Mary Magdalene, was the first person to see the risen Christ! Her steps so far...she was first to arrive at the tomb, she returns to find Peter and John in case something horrible was happening; they race ahead of her and are gone by the time she returns to the tomb; she is left alone and deeply upset; she sees a friendly face who may be able to assist her in the hunt for Christ's body.
We do not know why she didn't recognise Jesus instantly. It could have been because she was so upset; it could have been that her eyes were set on the empty tomb ('she turned'); it could have been that Jesus, in His resurrected body, had changed in some ways. Only when He spoke did she recognise Him. It is often by our voices that we are known! It was also likely to have been that He knew her name and the way in which He said it.
Jesus encourages Mary Magdalene to resist touching Him. Simple enough, but very soon we will read of Jesus inviting Thomas to touch Him and we have a similar invitation to the other disciples recorded in Luke 24 v 39. Now, there are two possible answers here: 1. That the other cases are to encourage His followers not to fear. John makes no mention of Mary's fear, only her joy. 2. That the Greek has been mistranslated from the original Aramaic which Jesus spoke in, so that 'Do not touch' is really 'Do not fear'.
Mary returned to the disciples exclaiming: ''I have seen the Lord!'' This is the core of Christianity, one telling another of their spiritual experience. If we have seen the Lord we have received something incredible and why not tell others about it?