The put-upon heroines of puffy-eyed potboilers used to be "by love possessed." Now we have new possessions.

In "Secrets," ABC's Sunday Night Movie, Andrea Fleming is so disturbed by the death of her possessive mother that she turns into an instant nymphomaniac. In "The Spell," part of NBC's Sunday night "Big Event," fat little Rita Matchett is so irked by cries of "Tubbo" from classmates that she starts tossing off hexes that kill people.

"Secrets" is a luridly entertaining two hour eyerow-raiser, airing at 9 p.m. on Channel 7."The Spell," a lame and shameless imitation of the hit movie thriller "Carrie," can be seen at 8 p.m. on Channel 4, for 90 primarily ridiculous minutes.

Noel Coward wrote, "How potent cheap music is," and cheap melodrama can have its charms too; thus are so many TV programs born-again B-movies. What saves "Secrets" from being glib and fitfully tawdry exploitation of an hotsy totsy subject is chiefly the performance of Susan Blakely as Andrea, her first big TV role since being killed off, at her request, from "Rich Man, Poor Man."

This isn't what you'd want ot risk calling a great job of acting, but Blakely is certainly and consistently watchable. Her pouts, frets and tears are enigmatic to say the least; she's a thawed Faye Dunaway, aloof but reachable. And as she goes about seducing everybody from her kid sister's 17-year-old boyfriend to a blind piano tuner, Blakely does convey both the desperation of people helpless before impulse and the undeniable thrill that a child gets from being very naughty and knowing it.

The character's mad outbreak of indiscriminate whoopee is triggered by the death of a mother who had taught her religiously to follow the old values and old rules of sexual conduct for proper young ladies. "Nobody believes that yuck any more," notes the younger sister. Why sis never developed the princess syndrome so ingrained in Andrea is one of those little details that the James Henerson script doesn't supply.

It is a screenplay, though, much more interested in effects than in causes. The causes are knocked off with a few top psychological California truisms - be yourself, don't repress your feelings, and all that. Ah, but the effects! Blakely standing naked in front of the piano tuner is sensationalism bordering on black comedy, and the fact that this is television, and we are all curious to see "how far" the scene will go, gives this and all of Blakely's overtures and fantasies the kind of titillating tensions a hard-core porno movie could never precipitate in a theater.

How far? No very far. Just far enough to be fun and frustrating at the same time. Just far enough to pretty much guarantee that "Secrets" will be a lollapalooza in the Sunday night ratings.

Director Paul Wendkos may have gone too heavy on the horrific shock effects - the dead mother keeps reappearing until exorcised - and the film really doesn't need them. What needs them is "The Spell" on NBC, a shocker so slackly sleazy as to make "Secrets" look like high Greek tragedy by comparison.

"Spell" starts out in a girl's gym class, just like "Carrie," except that, this being television, we don't follow the girls into the showers. In the gym, nasty Jackie is taunting hefty Rita about being such a fatso. Nasty Jackie climbs a rope. Nasty Jackie has a greatfall. Wicked Rita flashes a Linda Blair smile. And off we go down the old demon trail again, with not a single fresh or redeeming variation along the way.

Brian Taggert's script is not only slipshod but absentminded. One character is done in before we have any idea what her relationship is to other characters or to the plot. It's old Mrs. Bellamy. She walks down the stairs, sticks out a black tongue, blinks white eyes, begins to swell and smoke, and crashes through a window. Her splashy demise is the film's most picturesque burst of ghastliness, but one has no idea who the dear lady is.

The script also has the distraught mother, played with no distinction by Lee Grant, seeking counsel from a parapsychologist for her stricken daughter. But the glib twist ending makes this scene completely illogical. There is a requisite clockwork shock just before each commercial, but director Lee Phillips just lets things wander until each one comes along.

By the time fatty daughter and psychic mother meet for an unintentionally hilarious battle of the hexes - a round of dueling cantos that starts in the kitchen - one couldn't care less if good or evil will prevail. We know that what prevails here is mediocrity.

Unlike "Carrie," NBC's "Spell" never bothers relating any of its snappy horrors to the real if prosaic fears and doubts associated with the dread puberty years, or to the capability for cruelty among children. The whole thing might as well be taking place on Saturn.

ABC's "Secrets," despite its sesationalism, does have moments that illuminate certain dark corners of the American Dream, and though what it says about changing sexual roles and relationships is hardly revelatory, it will probably make "Secrets" seem, in five or 10 years, to have been an essentially sensitive sign of its times. That is an accomplishment for a television program.