Having heard the phrase, faint heart never won fair lady for the third time in very short span, i'm determined to find out its origin. Unfortunately, when i google, i'm getting a bunch of low-q Ladies is the plural form of lady, so the apostrophe goes to the right - ladies'.

For work-place specific gender-neutral politically-correct terms refer to the answer by @third-news. Otherwise, as elliot frisch has suggested, lady is the term you want. But in my opinion, if you're … I have always tried to understand the use of the word handsome in letter to a lady friend, but refrained from doing so, because i didn't know whether the word would be a thoughtful gesture or insulting.