Kat was a relatively blurry figure before her appointment as governess at the court of King Henry VIII was established. She is thought to have lived a relatively quiet life with her family until 1536, when she was appointed as a waiting gentlewoman for Elizabeth - who was then known as Lady Elizabeth, since Anne Boleyn had been recently executed and she was declared a bastard. It is unclear whether or not Kat had known Anne Boleyn personally before her beheading, but it seems that, later in life, Kat held Elizabeth's mother in high regard and wished to keep her memory alive in Elizabeth's mind.
Elizabeth's primary governess was Lady Bryan, but after the birth of Elizabeth's half-brother Prince Edward, Lady Bryan was taken away from Elizabeth to serve solely the new baby Prince. At this time in 1537, Kat became Elizabeth's primary caretaker, and it is then (with Elizabeth being roughly four years old) that their close relationship began to form.
Kat spent hours teaching Elizabeth everything that a lady (and a Princess) should know - geography, mathematics, writing, reading, languages, sewing, needlework, riding, dancing, etc. - and Elizabeth would later say that Kat took "great labour and pain in bringing of me up in learning and honesty."
In 1545, Kat married Elizabeth's senior gentleman attendant (and Anne Boleyn's cousin) Sir John Ashley (pictured below). At this time, she was around forty years old and passed the age of easily bearing children. She is said to have been very in love with John, however, and content to live with only him - feeling that Elizabeth was her child in a way, she already felt like a mother.
So, Kat Ashely certainly lived an eventful life. In many ways, she should be admired. She was hardworking, loving and affectionate in a time of terrible cruelty and danger. She found love later in life and had a faithful, devoted husband who loved Elizabeth just as much as she did. Although she had no children of her own, she always considered Elizabeth the only daughter she needed, and it is clear that the feeling was mutual. Later in life, Elizabeth would say, "Anne Boleyn gave me life, but Kat Ashley gave me love."