The teleplay is called "Bernadette" in the credits, with no reference to the movie and book Song of Bernadette. There is, however, clear evidence that the teleplay borrowed visually and musically from the movie Song of Bernadette.
The teleplay is based on Mary Gray Blanton's biography of St. Bernadette called Bernadette of Lourdes (later published as The Miracle of Bernadette). It uses many techniques of compressing the story to fit in less than one hour, which greatly lessens the accuracy in the portrayal. While the story is there, the details are not all that reliable. Some scenes are combined for greater dramatic effect.
Pier Angeli was 26 when she portrayed the 14 year old St. Bernadette. This is quite obvious in the teleplay, but her portrayal is still not without merit.
It was certainly a noble venture to retell the story during the 100th anniversary of the apparitions (this was produced and shown in 1958), but you are much better off watching one of the movie versions.