IF nothing else, "Fedra, the Devil's Daughter," is proof positive that a woman scorned can be awfully hard to handle. The sultry heroine of this moody and obvious Spanish drama, which came to the World Theatre yesterday, is an untamed soul who resists the advances of every male in her fishing village but finally marries a rich widower because she has eyes for his handsome son. These are points that are made clear early in the proceedings. Thereafter, "Fedra" is in a mess that would make a soap-opera librettist envious. Unfortunately, the lady's problems are not too dramatic or complex. Chances are a viewer will get the idea, even if he is not moved, long before "Fedra" does. The camera does capture lovely vistas of curving beaches, storm-tossed seas, crags and stolid but colorful fisherfolk. But there is very little that is special about the histrionics projected against these striking backgrounds. Enrique Diosdado is simply proud and stiff as the widower and Vincente Parra is haughty and confused as his blond son who rebuffs "Fedra." But Emma Penella, the harried brunette and dark-eyed "Fedra," enriches the scenery, if not the script. After all those poses of this well-endowed charmer in wet and dry décollétage, an observer can't blame the villagers for making a fuss about this unfair competition.