Tammy Mae Burke was babysitting in a car parked outside a Prince George's County laundromat when she gulped about six ounces of 151-proof rum. Before dawn yesterday, the 13-year-old girl was dead, the victim of an apparent overdose of alcohol.

"We had it in the car," said Tammy's older sister Brenda. "We kept telling her not to mess with the stuff."

But while Brenda and a cousin did their wash inside the laundromat, they said, Tammy sneaked a few swallows from the nearly empty Barcardi bottle.

"All they tell kids is not to use marijuana," Brenda Burke said yesterday. "Marijuana, marijuana, marijuana. They don't tell kids that drinking kills."

Physicians and alcoholism counselors said the older Burke girl is right. Youngsters routinely are warned against the dangers of alcoholism and driving while drunk, but they aren't told how to drink safely, and three or four children in the Washington area die each year as a result, counselor David Ennis said.

"What (Tammy) drank is lethal," said one coordinator of a Montgomery County detoxification center. "We talk a lot about alcoholism and the illness itself, but we don't talk much, especially to young people, about the acute effects of one intoxication from the drug.

"You don't have to be an alcoholic to die from alcohol."

Police told Tammy's sister that the girl had a blood-alcohol level of .46.

That means almost one-half of 1 percent of her blood was pure alcohol, more than enough to kill the average person.

"The textbook levels for fatal are anything above .4 and we've had them die at less than that," District of Columbia medical examiner Brian Blackbourne said. "The breathing and the heart are slowed to the point that the brain does not get oxygen -- and it's all over."

Rita Fowler, Tammy's cousin, said she and the two sisters went to the Westinghouse Laundromat at Marlboro Pike and Viceroy Street late Thursday with four baskets of clothing.

While the washers were running, the two older women went to a nearby "7-11" for soft drinks. The 13-year-old, Tammy, who lived in Nebraska and was visiting her father and sisters here, downed "three-fingers-full" of the potent liquor from the bottle, Brenda Burke said.

"When we found out she was drunk, we started laughing at her," Fowler said. "She was her usual playful self. She knew what it was, she's like any other child. She probably just wanted to find out how much she could take."

Tammy was noticeably drunk by the time Fowler and the older Burke returned to Fowler's car. With outstretched arms, the girl giggled and told her sister, "Brenda, I love you. Come here and give me a big kiss."

They returned to the father's apartment at 2729 Loring Drive in Forestville, and Tammy was left sleeping in the car. They told her father she was asleep in bed. The time was 1:49 a.m.

About 3 a.m. one of the young women checked on Tammy and felt no pulse. The other sister applied mouth to mouth resuscitation, and the girl was taken to Andrews Air Force Base Hospital, where she was pronounced dead at 5 a.m.

Doctors had not determined the exact cause of death yesterday, but they presumed an alcohol overdose. It is a little-known danger of drinking in younger circles, doctor said yesterday.

In December 1978, a 15-year-old Fairfax youth died after drinking several 8-ounce glasses of mixed spirits.

At Suburban Hospital in Bethesda, the emergency room admits an average of two juveniles a month who have consumed dangerously high quantities of alcohol. Other adolescents are treated and released because their drining is less serious, a spokeswoman said. One physician at Arlington Hospital said the major problem is the youths' lack of knowledge that too much alcohol too quickly can actually kill.

"Kids really don't realize this," said Dr. Charles Smith, medical director of Arlington Hospital's alcoholism treatment unit. "They're not told, and they see alcohol in the home all the time. They need to know more about the physiological effects of alcohol itself."

The psychological effects are similar to those of a barbituate or depressant. Smith said if a person drinks an ounce of 100-proof liquor every 90 minutes, the alcohol content in the blood will not rise. But Tammy Mae Burke drank about 6 ounces of 151-proof -- the equivalent of about 9 ounces of 100-proof -- in just a few minutes.

The Burke girl had not experimented with drugs before, her sister said.

"She was a strong person. She didn't take pills, she didn't drink. She didn't do that stuff," Brenda Burke said.

"Nobody ever said if you drink alcohol straight it will kill you. Jesus Christ! If I had known I would have taken her to the hospital immediately."