Who is the original composer of Ave Maria? And who is the girl that sings in it with that angelic voice?

The oldest arrangement I know of is by Guilo Caccini (1545-1618)
Here is my favourite version sung by Sumi Jo :

http://www.youtube.com/watch?v=fjZ8fBGtM...

Other famous arrangements are by Schubert and Gounod/Bach but these are later arrangements. There have been numerous melodies composed by lesser known composers which probably pre-dated Caccini but I can not find their names and dates.

Which version are you speaking of? Thousands of singers have performed countless arrangements/settings of Ave Maria.

Caccini was definitely not the first composer to do a setting of Ave Maria. Arcadelt, Josquin Desprez, Palestrina, and Lasso, for example, are all Renaissance composers who predated Caccini and wrote settings of Ave Maria.

At the beginning of John Q (the movie with Denzel Washington), there is a version of the song has always moved me. It has to be the most angelic, most calming, tear evoking version out.
It is hard to find, but it is sung by Ana Maria Martinez.

There are tons of versions of Ave Maria. Is the singer you are thinking of Charlotte Church? She used to sound beautiful when she was younger.

It's not by Caccini. It doesn't sound anything like his other music (I haven't actually heard because I do not like very many reinassance composer Josquin and Palestrina being to obvious exceptions). It's by a guy named Vladmir Vavilov who was known to play hoaxes. He put it as anon, but it somehow got Caccini's tag on it. By the way it's not one piece. My favorite is Josquins Madrigal Ave Maria, but Schubert did it and Gounod based his off a Bach piece, but Bruckner, Holst Mendelsson and even Verdi has a piece by that name (quite a few more too).

The 'Ave maria' is a hymn of the Roman Catholic church and settings go back even before Victoria to the days when Gregorian and other chants were the usual form of music in church services.

"Ave Maria" is a popular and much recorded m茅lodie.

It was composed by Gounod, based on the harmony and texture of J.S.Bach's Prelude No.1 in C Major from Well-Tempered Clavier Book I. It is a setting of the standard Latin Ave Maria text.
Schubert's version is the most famous for singing opera style.

The original composer of Ave Maria? Unfortunately, the Ave Maria text has been set to far too many different melodies, by far too many composers for any of us to figure out who was the "first."

I have no specific titles/occasions to cite, but I'm sure there are settings of Ave Maria in medieval masses.