Mom takes a quick belt in "the little girl's room." Mom passes out on the bed. Mom is found collapsed on the floor with an empty bottle by her side. There is crying from Mom's room in the middle of the night.

Once again, as so encouragingly often in the past, an ABC "Afterschool Special" takes a hard-core social problem and turns it into strong, believable and emotionally unimpeachable drama. "She Drinks a Little," at 4:30 today on Channel 7, is concerned not only with the problem of alcoholism, but also with a wrenching childhood trauma: being ashamed of a parent.

The parent in this case is a divorced mother who takes refuge in the skids; the one who suffers most from her addiction is a bright and beautiful teen-age daughter who tries subtly to request that Mom not attend the school open-house and asks a boyfriend not to come home with her to help her rehearse for the school play. MOM might be there, drunk and disheveled; she might do something horribly embarrassing.

And she does, finally, in a mortifying public scene after the curtain comes down on the play's performance. The daughter learns about a group called Alateen for the children of alcoholics and hears advice on how to deal with this illness afflicting her mother -- like, "don't clean her up, don't pick her up" when you find Mom sprawled on the dining room floor after a colossal bender.

Paul W. Cooper wrote and Arthur Allan Seidelman directed this special (which, like many of the best in the series, is from Martin Tahse Productions) from a book by Anne Snyder. The only fault to be found is in curiously abrupt editing transitions between a few scenes -- and the fact that not everyone watching the program, and finding the circumstances familiar, has access to the kind of group that comes to the heroine's aid.

But the two key performances are achingly sensitive and convincing -- a beguiling young actress named Amanda Wyss as daughter Cindy and a commanding older actress, Bonnie Bartlett, as the mother. The film has a tone, texture and sense of everyday home life far grittier and more realistic than on most prime-time television shows. "She Drinks a Little" is yet another feather in an already crowded cap for the ABC Afterschool Specials.

The specials are scheduled by the network to run on occasional Wednesday afternoons. But Channel 7 here, in order to accommodate its profitable afternoon strip of butchered and ravaged old movies, is delaying this week's special, and those slotted for Oct. 14 and Oct. 28, to Fridays. It was "a management decision," a station spokesman says -- and a bad one.