Musimbi received her BA in Linguistics and Religious Studies at the University of Nairobi, Kenya and her MA and Ph.D. in Linguistics at the University of Texas. She was Visitng Scholar in Hebrew, Greek and Exegesis at Harvard Divinity School. She received her Doctor of Ministry from San Francisco Theological Seminary.

Musimbi was Executive Secretary for Women in Church and Society with Lutheran World Federation in Geneva Area, Switzerland. She was General Secretary [CEO] World YWCA, Geneva Area, Switzerland, the first non-white woman to hold the role. Transformed the World YWCA into a young-women-led organization, with young women under 30 making up 55% of the Global Board of trustees. She also became Director of Population and Reproductive Health with the David and Lucile Packard Foundation in the San Francisco Bay Area. Musibmbi followed as President & CEO of Global Fund for Women.