Callen was born and raised in Nyamira County, Western Kenya. She attained her Certificate in Deacon Work from Ogango Deaconess Training College. She started giving back to the community by being an Instructor at Ogango Deaconess Training College. Later she worked as a youth counselor in Nyamira and Mombasa parishes.

Callen also worked as a youth counselor at Compassionate Social Care Organization in Love School Center.

She joined St. Paul’s University and earned a Diploma in Community Development.

Callen joined the organization in August 2017 as an intern and started working as a caseworker in January 2018 in the Secondary Department. Due to her love and passion for children and youths, she believes that NRCF is the best place to exercise her knowledge and skills. It touches her heart to see the lives of young ones transform.