Hamilton County Prosecutor Joseph Deters said Wednesday that 21-year-old Jessica Gamble of Springfield Township in suburban Cincinnati was indicted on child endangering and other charges.
The video shows the child handling and puffing on a marijuana cigarette.
Investigators say Gamble gave the girl the marijuana at their home sometime in August and that a person they haven't identified gave a copy of the video to the state family services agency.
Prosecutors say that, at one point, Gamble could be heard on the tape coaching her daughter.
"What's quite disconcerting," Deters remarked at a news conference, "is she's (the girl) handling this as if she's done something like this before.
"And thankfully, someone saw it and forwarded it to another cell phone. … And I'm just grateful that somebody in the community was savy enough and smart enough and cared enough about this little girl that they forwarded it to another phone and brought it to the authorities."
Gamble remains in jail. She could be sentenced to up to 11-1/2 years in prison if convicted of all charges.
The child is being cared for by her aunt, who says she is doing fine.