I beg you to click on Poseidon's Underworld hysterical blog recap of the 1979 melodrama/love story called THE PROMISE.
The film's love birds are Stephen Collins (TV's Tales of the Gold Monkey; 7th Heaven) and foxy Kathleen Quinlan (Lifeguard; Twilight Zone: The Movie 3rd segment 'Helen Foley/It's a Good Life remake).
Beatrice Straight ("Dr. Lesh" from Poltergeist) is the evil mom of rich boy Collins who hates his commonor girlfriend (Quinlan is hagged up in the first half). Mom pays for Quinlan's post-car accident facial surgery if she vows to stays away from her son. And then the drama begins...
Melissa Manchester sang the theme song ('I'll never say goodbye"). 1979 was big for Missy - she also did the Ice Castles film theme. Now that I think of it - the two '79 films would make a great tortured love double feature.
Please have a peek at this recap of The Promise: