NEW YORK -- “Wahala” by Nikki May (William Morrow/Custom House)The African word “wahala,” used commonly in Nigeria, means trouble and that's just what happens when three Anglo-Nigerian best friends in their 30s add a fourth woman to the mix.Boo, Simi and Ronke are longtime friends living in London. Boo is married with a young daughter, frustrated with the responsibility of being a mother, easily annoyed by her doting, cheerful husband, and then guilt-ridden for those feelings. Simi has a long distance marriage because her husband lives in New York.