Everyone in the neighborhood, it seemed, knew what the girl was up to, her mother and sister said yesterday. Once a good student, bright when it came to mathematics, she began cutting classes. She slept the day away and stayed out all night. In the wee hours of the morning, just before sunup, she would knock on the door of her family's Northeast apartment in the Trinidad neighborhood near Gallaudet University, waiting for someone to wake up and let her in.

"People that she was with, they said she was hitting the pipe," the girl's 15-year-old sister said when she and her mother, 34, were interviewed. (The names of the mother and her family are being withheld because of the ages of the children involved.) It may have been crack cocaine. It may have been PCP. Whatever drug it was, it transformed the girl into a sullen, violent person at the age of 12.

The girl's trouble with drugs began last summer, her mother said. In the fall, a social worker tried to have the girl admitted to an in-patient drug treatment program at St. Elizabeths Hospital. But there was a waiting list of about six months. In counseling with the social worker, the girl was uncooperative. And sometimes her mother would not follow through with appointments.

Tuesday, the girl allegedly took her mother's starter's pistol and tried to rob a neighborhood dry cleaners. Yesterday, the girl, who has been charged with assault with intent to rob, was ordered held at the Receiving Home for Children.

"Had we gotten {the girl} into the in-patient right away, things would have been better all the way around," said the social worker, Sally Bird. She works for the Junior Citizens Corps, a Northwest Washington community service organization.

After attending the girl's hearing at D.C. Superior Court yesterday, the woman said her daughter will be able to go home on weekends. The woman said she was annoyed by the court process, especially by the fact that someone mentioned during the hearing that they had smelled alcohol on her breath.

When she picks her daughter up from the Receiving Home on Saturday mornings, she said, "They're going to have somebody observing me because they smelled alcohol on my breath. I had a beer. One beer."

In an earlier interview, the mother said she feels partly to blame for her daughter's problems. With cooking, cleaning and taking care of her four other children -- ages 16, 15, 11 years and 17 months -- she could not keep up with her 12-year-old's activities. She supports the children on public assistance. She said she is divorced from the girl's father, who lives in Alexandria.

"I should have put my foot down," she said. "I'm the one who made the mistake. If I had put my foot down, she wouldn't have gone around with the wrong crowd of people."

The woman and her children live in a small upstairs apartment on 16th Street NE. The cramped apartment is in a state of disrepair. There is a large hole in the ceiling over the stove. Valentines and family pictures adorn many of the walls in the apartment, along with a letter from the 15-year-old's high school that praises her for being on the honor roll this year.

Asked about the last time her sister attended classes at her school, Samuel Wheatley Elemetery, the 15-year-old thought for a minute and said, "It's been so long ago." Maybe November, she said.

"She used to sleep in the daytime and go out at night," the 15-year-old said. "She started getting violent. Her hair started falling out. She didn't care. She'd wear the same clothes every day . . . . She's good in math. She can do some math, quicker than I can. She used to love school."

"Love it," the mother said.

Her mother said that teen-agers in the neighborhood, maybe even some adults, helped her daughter get involved in drugs. When she learned that the girl was using drugs, she said she asked people on the block not to help the girl in any way. One man used to give the girl money for helping him pick up litter on the street. The mother asked him to stop so the girl wouldn't have money to buy drugs.

Not everyone would cooperate, the mother said. She let her 15-year-old do the explaining.

"My mother would tell them 'Don't let {the girl} go with you nowhere. Don't give her cigarettes or money,' and they would give it to her anyway."

"I love my children," the mother said..

The 15-year-old said her little sister used to hang around with people who sold drugs. She suspected it was crack cocaine. She described the small vials containing tiny chunks of the hardened form of cocaine that are commonly sold on the streets.

"She used to be with people who sell it," the 15-year-old said. "They used to sell soap and trick people."

Bird, the social worker, became involved in the girl's case last fall. After she was unable to have the girl admitted to the treatment program at St. Elizabeths, she had the girl attend counseling sessions with the Junior Citizens Corps. The girl was not cooperative.

On a couple of occasions, Bird picked the girl up at home and took her to the sessions. Once, the girl was wearing a beeper. "She had around her neck what I learned was a beeper," Bird said. "A beeper is what the children use when they're selling for a dealer."

Because the counseling outside the girl's home did not appear to be working, Bird suggested to the girl's mother that counseling take place at home.

"I offered to do the counseling at home, and the mother just didn't want that . . . I did begin to feel it was a little neglectful because I just felt like there wasn't enough motivation on the mother's part or perhaps she was helpless. She was frustrated."

The mother "is doing what she can," Bird said. "I think that she needs a lot of things, a lot of help."

The mother said she kept a starter's pistol around the house for protection. She knew it would fire only blanks, but felt it looked real enough to be a deterrent. At some point, the 12-year-old reached atop the hutch in the green living room and took the gun. The woman said she did not know the gun was missing.

Tuesday, the girl slept through the morning and then went out. She returned later in the afternoon. "She came here in the bathroom crying, saying, 'Momma, I want some help' . . . . She said, 'Momma, I'm ready to go to the doctor for drug treatment,' " the mother said.

The mother did not know what prompted the girl's plea. But a short time later, police arrived. The girl had been identified as the person who pointed a gun at the owner of the Peerless Cleaners at 1202 Bladensburg Rd. NE, police said. The owner knocked the gun out of the girl's hand. The girl attacked the owner and scratched her face.

The mother took the girl to police later that evening. "I told her to get dressed and look decent," she said. The conversation with police ended, she said, when an officer concluded: "We got to book her."

The girl has been held at the Receiving Home since her arrest. During visits with her mother, she says she is sorry for what she did, her mother said. "Of course she is. Yeah, she's sorry. That's why she was crying -- acting just like a baby, like a newborn baby. That's how she cries."