Catherine received a good education at a time when the king's followers were turning in his wake from the ecclesiastical domination of education to what was described as the "new learning. "
In the summer of 1544 Henry took the field for a campaign in France, appointing Catherine as regent to rule England in his place. She carried out her duties with competence, attending to the finances of the realm and supplying Henry's armies with men, supplies, and provisions.
Parr's sympathies for the new reformed faith, however, made Catholic courtiers hostile to her, and their machinations with the king put her in danger. She was guilty of debating religious issues at court and encouraging commoners to read the Bible in an English version, an act that constituted defiance of the king as the supreme head of the church. An arrest warrant was issued but on the eve of being taken prisoner Catherine soothed the king's ego with submissive and penitent speeches; when palace guards arrived to take her prisoner the king sent them away.
In the last year of her life she wrote A Lamentacion or Complaynt of a Sinner, which was published shortly after her death.
Catherine married twice, the first time to Lord Edward of Borough. After his death, she married Baron John Neville, who died in 1543. Although she was drawing close to Thomas Seymour, the brother of the king's late wife Jane Seymour, Henry himself proposed marriage to her. She accepted the proposal, and the sixth royal wedding of Henry's reign took place on July 12, 1543, at the palace of Hampton Court. She became a widow for the third time in January 1547. After Henry’s death Catherine married a former suitor, Thomas, Lord Seymour of Sudeley, who was admiral of England from 1547 to 1549, but she died shortly after giving birth to a daughter.