She showed, but everyone could tell.

A 3-year-old girl arrived at her Harlem day care center Friday reeking of weed and carrying 14 bags of marijuana in her pink Minnie Mouse backpack, cops said.

But the girl — the niece of Ramarley Graham, the unarmed teen tragically slain by a cop’s bullet last year — is no pint-sized pot dealer, officials said.

A friend of the tot’s dad, Graham’s brother, was arrested after admitting the marijuana was his, according to authorities.

The illegal version of show and tell unfolded around 1 p.m. when the girl got to the Early Life school on W. 147th St. near Eighth Ave. Day care administrators called police, who found a “substantial” amount of marijuana in the child’s backpack.

The girl was questioned and returned to her parents. A brief investigation revealed the pot belonged to 24-year-old Kelly Mena, who was charged with criminal possession of marijuana and criminal sale of marijuana, cops said.

It wasn’t immediately clear who put the drug in the girl’s backpack and why. Police sources said the 3-year-old’s father is Francelot Graham Jr., 27, Ramarley Graham’s older brother.

Graham, 18, was killed by cop Richard Haste on Feb. 2, 2012, after police pursued him into his family’s Williamsbridge home during a drug investigation. Once inside Graham’s home, Haste identified himself as a cop and fired at the teen at point-blank range in a bathroom, officials said.

Graham was unarmed. Police later claimed Haste erroneously thought he saw a gun. Cops found a bag of marijuana near Graham’s body and suspected he was trying to flush it down the toilet when he was shot. Bronx prosecutors indicted Haste on manslaughter charges that June, but a judge tossed the case because an assistant district attorney made a mistake when presenting the charges to the grand jury.

Bronx Supreme Court Justice Steven Barrett gave the Bronx district attorney’s office leave to try again, but a second grand jury opted against a manslaughter indictment in August.

Federal prosecutors said in August that they would review Graham’s case to determine if his civil rights were violated. Graham’s father, Francelot Graham Sr., denied any knowledge Friday evening of the marijuana discovery.