As in Sunday's blast, her bomb was rigged with shrapnel that caused severe injuries.
Chechnya has become more stable under the grip of its Moscow-backed strongman, who incorporated many of the former rebels into his feared security force. But in Dagestan, the province between Chechnya and the Caspian Sea, Islamic insurgents who declared an intention to carve out an Islamic state in the region mount near daily attacks on police and other officials.
Rights groups say that authorities' tough response involving arbitrary arrests, torture and killings of terror suspects has fueled the rebellion.
The Kremlin replaced Dagestan's provincial chief earlier this year, and the new leader abandoned his predecessor's attempts at reconciliation and his efforts to persuade some of the rebels to surrender in exchange for amnesty.
Security camera images broadcast by Rossiya 24 television showed Sunday's moment of explosion, a bright orange flash inside the station behind the massive main gate followed by plumes of smoke.
"All the doors, windows scattered. I got a concussion and smoke billowed from inside.
Another witness, Roman Lobachev, told Rossiya television that he was putting his bags on a belt for screening when he heard the sound of an explosion. "I heard a bang and felt as if something hit me on the head," said Lobachev who survived the attack with minor injuries.
The bombing followed Friday's explosion in the city of Pyatigorsk in southern Russian, where a car rigged with explosives blew up on a street, killing three.
Following Sunday's explosion, the Interior Ministry ordered police to beef up patrols at railway stations and other transport facilities across Russia.
Russia in past years has seen a series of terror attacks on buses, trains and airplanes, some carried out by suicide bombers.
Twin bombings on the Moscow subway in March 2010 by female suicide bombers killed 40 people and wounded more than 120. In January 2011, a male suicide bomber struck Moscow's Domodedovo Airport, killing 37 people and injuring more than 180.