ASSUME FOR a moment that your mother has just announced that she, after raising you to a more or less healthy adulthood and then divorcing your father, is a lesbian.

Upon learning this, you: a) freak out, suddenly questioning your own sexuality; b) conspire with your siblings to recruit another lesbian to seduce your mom's new girlfriend, thereby sabotaging their relationship; or c) when that last ploy doesn't work out, make a play for the girlfriend yourself. If you think any of these options are, under the circumstances, the least bit natural or, barring that, funny, you'll probably enjoy "My Mother Likes Women," a Spanish comedy-drama about three grown sisters encountering just such a scenario.

Designed mainly for an audience for whom the sight of two women holding hands still seems alien or a cause for tittering, it is intended to be, by turns, screwball and heartwarming. If, however, the idea of, say, even gay marriage at this point feels a little been-there-done-that, it will mostly be as annoying as heck.

Which is not an emotion that one expects to encounter in a sugary confection like this, even one in which first-time writer-directors Ines Paris and Daniela Fejerman have ensured that, as an added bonus, each of the sisters will wind up not only with a newfound tolerance for homosexuality, but a new lover herself. (Males, all of them, incidentally. We wouldn't want the movie to be too gay-friendly, now would we?)

Gag me with a spoonful of flan.

Told mostly from the point of view of Elvira (Leonor Watling), a ditsy -- no, make that obnoxiously neurotic -- aspiring writer with two sisters (Silvia Abascal and Maria Pujalte), the cliche-fraught "My Mother" wastes no time jumping into the fray. Within minutes of the daughters assembling for a casual family gathering, materfamilias Sofia (Rosa Maria Sarda) announces to them that she has a new love. But when they discover that their mother's silver-haired beau is actually a bodacious belle their age (Eliska Sirova), the three young women react badly.

That's putting it mildly.

The problem with "My Mother" is not, in and of itself, the premise. It probably is, even in this day and age, all too common for some folks to respond to the announcement of a relative's homosexuality with a mixture of horror, denial and hostility. What's troubling about "My Mother" is not the way the sisters respond to the news, but the way that Paris and Fejerman have opted to make lighthearted comic fodder out of the daughters' responses.

Mind you, I'm not arguing that they should have turned the story into a humorless PFLAG training video. No group, gays included, is exempt from satire. And it's clear that the real objects of ridicule are the silly sisters, who have yet to grow up.

What's wrong with the movie is that, if you're the least bit evolved already, Elvira's behavior (along with that of her irritating siblings) seems strangely out of sync with today's rapidly changing times. It comes across as less side-splitting than a sad reminder of the past.

MY MOTHER LIKES WOMEN (Unrated, 93 minutes) -- Contains obscenity, sex talk and sensuality. In Spanish with subtitles. At Visions Bar Noir.

Sofia (Rosa Maria Sarda, center) is in love with Eliska (Eliska Sirova) -- much to the dismay of Sofia's three daughters -- in "My Mother Likes Women."