Seems a lot like The Swan
with Grace Kelly and Louis Jourdanshare
Both were adapted from Ferenc Molnar's play, The Swan.
Just different adaptations of the same material.
Having just seen both on AMC, I have to say that the color version with Grace Kelly, Louis Jourdan & Alex Guinness is FAR superior in every way. The interplay in the last half hour between Agnes Moorehead and Alec Guinness is truly superb, and worth sitting through the rather slow-paced first hour or so. Guinness, of course, does his normal spectacular, understated performance -- once again reminding us of why he was a screen legend for half a century before Darth Vader wasted his talents.
I did not see the ending coming.