Cleopatra Thea - Basilissa of Basileía tōn Seleukidōn from 126 BC to 121 BC
Cleopatra Thea was the ruler of the Seleucid Empire from 125 BC after the death of Demetrius II Nicator, and until 121 or 120 BC, some of the time in co-regency with her son Antiochus VIII Grypus

She grew up in Egypt as the daughter of Ptolemy VI and Cleopatra II. In 150 BC she married Alexander Balas, but was later remarried to Demetrius II. He was defeated and captured by the Parthians in 139 BC, after which she married his brother, Antiochus VII Sidetes. When Demetrius II was released in 129 BC, she remarried him after Sidetes was killed in battle. In 125 BC, her son Seleucus V became king - but she had him murdered shortly afterwards, and ruled Syria between 125 BC and 121 BC - formally she shared the throne with her other son, Antiochus VIII Grypus

Grypus became less controllable as he grew up and in 121 BC Cleopatra Thea decided to eliminate him. As he returned from a hunt one day, she offered him a cup of wine. Since this was not common behavior for her, Grypus was suspicious and forced her to drink the wine, which killed her.
Cleopatra Thea
Queen Cleopatra Thea "Good-harvest" of the Seleucid Empire

Epithet: Eueteria ( "Good-harvest")

AE unit Antioch
Obverse: Radiate head of Antiochus VIII right
Reverse: Facing owl standing on amphora; BAΣIΛIΣΣHΣ / KΛEOΠATPAΣ // KAI / BAΣIΛEΩΣ / ANTIOXOY // ϘP
Ref: Houghton-Lorber II 2263