Her name is Gurumayi Chidvilasananda and she is the head of the Siddha Yoga Meditation Lineage.
She hasn't has a public satsang (gathering) since January 1, 2004. Every year, on New Year's day, she would broadcast her annual message via audio and video around the world to her devotees. The last one was on January 1, 2004.
She is NOT in hiding; she is accessible at her ashrams, it's just that she's not traveling and teaching publicly. It is believed that this is due in part to the fact that she feels that she has given all the teachings and talks that are necessary. This decision was made two years BEFORE "Eat Pray Love" was released and year or more after Liz visited her Ashram in India.
If you are interested in Gurumayi, a great place to start is her book Sadhana of the Heart: A Collection of Talks on Spiritual Life which is a compilation of these New Year's messages. This book has enough "messages" for a lifetime.