Both girls here are Kat, sorta.
The Dark Angel is a costume for Kat in the game but I believe the actual Dark Angel that shows up in the games, is what Raven and Kat both looked like when they were one being

Adding on to this since it seems the tags changed, the girl with the black hair is indeed not Raven and should not be tagged as such. Raven has pale skin with really long black and red hair. She also has blue eyes not red, go look at any picture of Raven and see she looks very different than the Dark Angel. Even the artist said this was two Kats, one in 2B cosplay and the other in Dark Angel cosplay.