A quick Google search seemingly answered the question: Courtenay Taylor, right? Not quite. Clicking on the immediately listed link, the voice actress' Fandom page lists her as voicing the Sole Survivor. Investigating further, as VAs often voice multiple characters, I looked at her list of credits, but Nuka-Girl was not one of them. Naturally, I then looked at the character page for Nuka-Girl. However, Fandom did not have any listing for a voice actress. Gamepedia's Nuka-Girl's dialoge page also lacked a VA credit, citing only this for her voice: "DLC04_Announcer_NukaGalaxy_NPCFNukaGirl".
Finally, it seemed like I found a potential voice actress at IMDb's Fallout 4 credit list, but none of the ladies credited with lending their voices to the Nuka-World DLC (Anjali Bhimani, Corri English, Laura Post, and Jan Johns) were credited as voicing Nuka-Girl.
After spending more time searching than I care to admit, I still don't have an answer to my question: Who voiced Nuka-Girl?