Adding another cross-link, as Priscilla Ahn also fits this thread perfectly, since OP said he listens to female vocals to chill: Singer-songwriters & One-man-bands
And on that note, the most chill female vocalist I’ve ever heard has to be Hope Sandoval, particularly her releases in the ‘Hope Sandoval and The Warm Inventions’ band format:
(Her ‘Mazzy Star’ work is more high-BPM and with more distorted guitar, distinctly less chill overall, but not without a few dreamy tracks of its own.)