The Nun and Yahar'Gul

Hey, bit of a slowpoke here working my way through my first playthrough still, and I had a question about Yahar'Gul and the Hypogean Gaol, and availability of the Nun character. Due to blundering around and needing to git gud still I ended up killing Rom before getting access to the Hypogean Gaol (I had to look it up to verify this). I sent almost everyone I found to the Chapel, except the old guy who kills everyone who I sent to the Clinic instead. Online it mentions a Nun character who is in Hypogean Gaol, I went by the area that seems to he where the Gaol is but she is not there. Did I just completely miss my chance to meet this last character? I could find no direct statement on her presence in Yahar'Gul, only her presence in the Gaol.