Barbara's father, Lord Edward Herbert, was a younger son of William Herbert, 2nd Marquess of Powis; he married Lady Henrietta Waldegrave, but died only a few months after the wedding, in 1734.

[1] On 30 March 1751, when Barbara was just fifteen, she married her kinsman Henry Arthur Herbert, who was in his late forties.

Together, Barbara and Henry were the parents of two children: In 1771, shortly before the earl's death, the family seat at Oakly Park was sold to Robert Clive, 1st Baron Clive,[3] and they moved permanently to Powis Castle.

A portrait of Barbara by an unknown artist, dated to approximately 1750, is held at Powis Castle, in the care of the National Trust.

[4] Through her daughter Lady Henrietta, she was a grandmother of Lady Henrietta Antonia Herbert (wife of Sir Watkin Williams-Wynn, 5th Baronet), Edward Herbert, 2nd Earl of Powis, Lady Charlotte Florentia Herbert (wife of Hugh Percy, 3rd Duke of Northumberland), and politician Robert Henry Clive.