He faces up to life in prison if convicted of murder.
Serou moved from California to Russia in 2019 to study law at Lobachevsky University in Nizhny Novgorod, news reports said.
Beccy Serou told NPR that her daughter was in a hurry to get to a clinic Tuesday and may have gotten into a passing car.
“I think that when she saw that the person wasn’t driving to the clinic, but instead was driving into a forest, she panicked,” Beccy Serou said.
ArLuther Lee contributed to this report for The Atlanta Journal-Constitution.