Probably not a Bovans Nera since they are not a typical hatchery bird, but you are on the right track. Bovans Nera is a specific type of Black Sexlink. This is where a female barred bird such as the Barred Rock is crossed with a brown or gold male bird, frequently a RIR or similar.
The chicks can be sexed at hatch since only the males will get the barring gene (from the mother) and will have a white spot on the tops of their little heads whereas the female chicks will be all black on the top of the head. It makes it easy to select and raise only the girls since they are raised for egg production.
So in a nutshell, I would call your new adoptee a Black Sexlink.
Enjoy her--they lay lots of eggs!