Is this Welsh princess the first British woman author?

From The Independent: 

Britain's earliest known woman writer is identified as a 12th century Welsh princess who died fighting the Normans. Princess Gwenllian, daughter of the King of Gwynedd, is said to be the author of the Mabinogion, the 800-year-old collection of Celtic tales of romance and adventure, whose unknown author has always been thought to be a man.

In his book to be published later this month, Dr Andrew Breeze argues that Gwenllian is the author of the Four Branches of the Mabinogi, the main tales of the Mabinogion, which tells of princes and princesses and daring deeds in a Celtic world of heroism, chivalry and magic.

Dr Breeze, a Celticist and English literature lecturer, says Gwenllian is one of the greatest writers. "It is sad to think that the remains of the finest of Welsh prose writers lies in an unknown spot in the battlefield where she was killed," he said.

read more here 

@ The Independent

@ Sacred Texts

@ The Mabinogian