Monday was the first day of trial for Natella Natanova, the sister of the woman accused of hiring a hit man to kill her estranged husband — a Queens orthodontist.

The Queens district attorney says Natanova approached the brother of the victim, Daniel Malakov, back in March and said, "You should know if you talk, you will be the next to go."

If convicted, Natanova faces up to four years in prison.

Her sister, Dr. Mazoltuv Borukhova, is charged with murder and conspiracy in connection with Malakov's death.

Malakov was gunned down execution-style in a Forest Hills playground last October, in front of the couple's young daughter. He had recently been granted custody after a bitter court battle, and was bringing the girl to see her mother when he was killed.

Prosecutors say Borukhova paid her uncle, Mikhail Mallayev, $20,000 to carry out the crime. Mallayev is also charged with murder.