She was the daughter of Sir Thomas Southwell (d. 1568) of Woodrising, Norfolk and his third wife Nazareth Newton.
There may be some confusion among ladies in waiting to Elizabeth and Anne of Denmark called "Mistress Southwell", including her niece Elizabeth Southwell who ran away from court and married Robert Dudley.
This Mistress Southwell came to court in January 1600, as a replacement for Margaret Radclyffe, and Rowland Whyte noted she would be sworn in as a maid of honour, "My Lady Newton having sought it for her daughter".
Moleyns, who was younger than his wife, was said to be notorious for his ugliness and was a veteran soldier weakened by his injuries.
[5] Rowland Whyte mentioned that "Lady Moleyns, she that was Mistress Southwell, the maid" came to the christening of Barbara Sidney, daughter of Sir Robert Sidney and Barbara Gamage, in December 1599 in the company of Anne St John, Lady Effingham.