Rebecca Naa Dedei Aryeetey, also known as Dedei Ashikishan, was a businesswoman, political activist, and feminist from Ghana who lived from 1923 until 22 June 1961. In Accra, she was well known for running a flour business. She appears on Ghana's 50 Pesewas coin as well.
Naa Dei entered the flour industry after finishing her primary education. From her flour business, she amassed such money and power that she was given the name "Ashikishan," which is a Ga term for flour. She was well-known for leading CPP women's activities at her home in Kokomlemle, Accra, and serving as the party's main financier at the time. She supported Nkrumah and the CPP party as a political activist for the CPP and was instrumental in Ghana's fight for independence.
That's all what I have heard about the picture on the 50 pesewas coin.