NASHUA, N.H. -- A baby sitter in Nashua was charged with felony reckless conduct after a child was rushed to a hospital after police said she overdosed on prescription medication.

Police said Esther Ngari, 20, of Kenya, was caring for the 18-month-old girl and her 6-month-old sister when the older girl opened a prescription bottle that did not have its lid on tightly. Investigators said the girl took some of the pills, but it wasn't until later that her father realized something was wrong.

The girls' father said that he became concerned when his daughter couldn't hold her head up or speak. Police said the prescription was an anti-seizure medication.

"The child suffered internal injuries from ingestion of the drug," Nashua police prosecutor Tim Goulden said.

Friends of Ngari said that she was distracted while trying to quiet the girl's sister. But police said she should not have left a loosely closed medicine bottle in the girl's reach.

"The analogy is the same as if you left a loaded gun and if a child gained access to it," Goulden said. "You'd bear responsibility for that."

The girl was listed in serious condition at Boston Children's Hospital.

Friends said Ngari agreed at the last minute to watch the children after meeting them and their father for the first time. She's in the country on a student visa and was visiting from Virginia.

"She didn't know the children, she didn't know the father," said a friend, Rebecca Wahoma. "He just left the children, and then he left."

Police said that it wasn't until the children's father picked them up that Ngari noticed her pills spilled across the bedroom floor, some wet and discolored. In the meantime, the girls' father called 911, and police were at Ngari's door shortly after.

"She thinks she's stupid," said Anthony Muitunga, a friend of Ngari's. "She offered to help with kids she didn't even know."

Ngari is facing a felony charge of reckless conduct and a misdemeanor charge of endangering the welfare of a child. She was being held on $50,000 bail.