My personal choice for 2008 Female Vocalist of the year is non other than Marie Digby. 

Marié Christina Digby (pronounced /mæɹi’eɪ ‘dɪgbi/ Ma-ree-AY Dig-Bee) (born April 16, 1983) is an American singer-songwriter, guitarist and pianist. She is best known for her acoustic cover version of Rihanna’s No. 1 hit “Umbrella“, which attracted attention on YouTube in 2007. The song was subsequently played on the radio station STAR 98.7, was featured on the third season opening episode of the MTV show The Hills,^[1] and peaked at #10 on the Bubbling Under Hot 100 Singles chart. Marie performed the song on the late night talk show Last Call with Carson Daly on August 2, 2007.

Marie’s first official single, “Say It Again“, was released to radio stations on January 18, 2008. Her debut album, Unfold, was released on April 8, 2008.

This song,  Say It Again (Original Version) brought her to fame….Take a listen .

and this version is the Official Release after she was discovered

This is another acoustic version of the song Girlfriend (Original Version)

Rihanna – Umbrella (Acoustic)