Is there a way you can find out what country or region of Africa you have links with? That way you can research girls' names used in that area, and maybe choose one that way.
I think that would be a better option than choosing a random African placename, personally.
Funny enough, the capital of the Seychelles (islands) is called Victoria ;) And Victoria is also the name of Africa's largest lake. Great name but probably not what you're looking for.
And Sierra Leone is the name of an African country.... both Sierra and Leone/Leona are actual names, but again, maybe too common for you?
For fun, here are some suggestions of placenames that may work:
Luanda (Capital city of Angola)
Praia (Capital of Cape Verde)
Niamey (Capital of Niger)
Malindi (city in Kenya)
Tiya (city in Ethiopia)
Harper (city in Liberia)
Kadoma (city in Zimbabwe)
Lomé (Capital of Togo)
Mara (small river in East Africa)
Shebelle (river which flows through part of Ethiopia & Somalia)
Tana (river in Kenya)
Didessa (tributary of the River Nile)
By the way, make sure you check out the literal meaning of any placename you're considering. Khartoum, for example, means "elephants trunk" :)
Also if it's a river/lake name, research its condition. You don't want to name a child after a river that might be extremely polluted or something.