First I heard "Still I Love Him" = this version of When I Was Single was from a recording in the late 1950s (best guess c. 1958 or '59. The original take may have been on Topic in England.

The singer was the unaffected, memorable Isla Cameron.

My guess is that, though the song is older, her lovely version was first to inject the song into the 1950s folk revival. Certainly many of us (yes, even us boys who could scarcely dwell in the female persona of the song) were singing it all over the place after that.

Bob