Beata Oxenstierna was born to Baron Erik Gabrielsson Oxenstierna (1540s-1594) and Bengta Gera. Her father had been a courtier to Princess Cecilia Vasa of Sweden, and governor in Swedish Livonia, and she was born in Reval in Livonia during his tenure as governor there.
She served as Mistress of the Robes to queen Christina of Sweden from 1639 to 1647. She served as maid of honor to the queen of Sweden, Christina of Holstein-Gottorp, in 1610-1613. Her spouse served as governor in Stegeborg 1615-1618, Norrköping 1618-1621, Kronoberg 1621-1626, and Östergötland 1627-1631.
Beata Oxenstierna was widowed in 1631.
On 2 February 1639, she was appointed mistress of the robes to queen Christina. The reason for splitting these two positions in four, was the wish that Christina should not be dependent upon one single individual and favorite.
In 1639, the position of Mistress of the Robes was thereby shared between Beata Oxenstierna and Ebba Ryning (though the former was given a higher rank), and the position of foster mother was shared by Ebba Mauritzdotter Leijonhufvud and Christina Natt och Dagestan Formally, however, also Leijonhufvud and Natt och Dag was given the title of Mistress of the Robes in name, though not in regard to their task.
Leijonhufvud was related to Councillor Oxenstierna by marriage, which is believed to have played a part in why she was given her position: Beata Oxenstierna and Ebba Ryning was also connected to the Oxenstierna party.
Beata Oxenstierna is described as: "A charitable lady, who did much good at court". With some exceptions, such as Ebba Sparre, lady Jane Ruthven and Louise van der Nooth, Christina did not show any interest in her female courtiers, and generally mentions them only to express contempt over their femininity and portray herself as more masculine than them. The more of them that comes here the worse it is".
She was granted two estates in 1646 and retired with a large pension on 6 July 1647.
