I've heard SFF sing before, she posted a self-rendition of "Yue Liang Dai Biao Wo De Xing" on her blog once and though it was an unprofessional attempt, she sounded alright.
The series she sings the themesong for, "Jiao Yi Sheng Ma Ma" is airing (maybe already finished airing) in China currently and has received very positive response, making it top of the viewers chart for last and this month. The story revolves around 2 sisters. The lead actress and sweet sister is played by Michelle Yip while the 2nd lead and evil sister is played by SFF, who ditches her sweet and gentle image for once. SFF has apparently received many praises for her convincing portrayal of a villian.