I had a few requests on this recently and felt it needed to be answered. I meant to do this a long time ago when I discovered this build but it just slipped my mind. Anyway, it looks like The Duke's Dear Freja can be killed (one-shot) outside of her boss room but still appears there at half health automatically.
You can support my Patreon if you are kind at heart, you've already proven that you're amazing just by coming to my channel. https://www.patreon.com/RayDhimitri
Ray Dhimitri presently has 28,732,479 views for Dark Souls II across 322 videos, accounting for over 2 days of watchable video on his channel. This is 24.59% of the total watchable video for Dark Souls II on Ray Dhimitri's YouTube channel.