Her father was Richard Knightley of Fawsley, Northants but I cannot find which of the many of these Richards he was.  However Leo van de Pas’ Genealogics site says he parents were Richard Knightley and Joan Skennard, whose name is given as Skymmerton in the 1564 Northants visitation and as Skenars als Skenerton of Aldrington, Northants in the 1881 visitation.  If this is correct, the 1881 visitation indicates that there was a double brother sister marriage with:

Richard Knightley, 1st s. marrying Jane dau. of Sir John Spencer of Althorp.
Susan Knightley marrying Sir William Spencer, son of Sir John Spencer of Althorp.

Both of these marriages are confirmed in the 1564 Northants visitation for Spencer, pp. 47-8.

Lipscomb merely shows her father, not her mother.