I don't know her name or anything about her; she could be a professional singer, even a famous Indian movie 'playback' singer -- or simply a devotee of Sathya Sai Baba who sings exquisitely
"Bhajans from Sundaram Group Chennai (Madras) - Part 1"
First bhajan on the video, Sathya Sai Baghavan
She sings again, musical intro starting at the 8:45 mark; Kesava Madhava.
Unlike the earlier bhajan she sang, the melody for this one at certain parts is excruciatingly hard to sing. She pulls it off -- effortlessly, which makes me wonder again if she isn't a professional, although I've heard professionals who couldn't get near her technical mastery, which is characterized by effortlessness.