Can you give an example of where you find this name in a "European" context?
All of the examples of women named Darnisha I was able to find going through the first four pages of the Google results for that name were African-American. In that context it is a 20th century creation, blending the start of names like
Darnell with -isha, which was the most productive suffix in newly created African American names in the 1980s and 1990s. (
Lakeisha, Denisha, Velisha, etc. being other examples.)