She has/had a relationship with WILLIAM I OF SCOTLAND.
She was the mistress of William I “the Lion” King of Scotland, son of Henry of Scotland, Earl of Huntingdon and Northumberland and his wife Ada de Warenne.
The Chronicle of Melrose refers to the daughter of Robert Avenal as the mother of King William's daughter Isabel.
The fact that her daughter was named Isabel has led to some confusion and the suggestion that she too is Isabel. This is unsubstantiated by any evidence.
There are no known dates of birth or death for this person. Knowing she was a mistress of William I “the Lion” King of Scotland and knowing that he was born in 1143, it is probable that she was about his age or likely younger so we will speculate she was born after 1143.
Cawley, Charles. "SCOTLAND UNTITLED NOBILITY, (Avenell)." Foundation for Medieval Genealogy: Medieval Lands, A Prosopography of Medieval European Noble and Royal Families. Accessed March 28, 2015. http://fmg.ac/Projects/MedLands/SCOTTISH%20NOBILITY%20UNTITLED.htm#_Toc389126067.