Google produced the following site with 4 matches. My bet is she remembers Dean Martin's version.

http://www.rockmine.music.co.uk/Lists/WhoSang/WhoSangL.html

>My mom has asked me to find out the author and who used to sing a song titled.... Let me go lover.
>I think it was popular in the late 40's or in the 50's. I've been to several web sites to no avail and I figured I would bring it to the greatest minds on earth. No really! :)