The following wikipedia article casts doubt on Gunnora's parentage:

All that is known of Gunnora's parentage is that she belonged to a family who had settled in the Pays de Caux. Robert of Torigni wrote she was a forester's daughter from the Pays de Caux and according to Dudo of Saint-Quentin she was of noble Danish origin. Gunnora was probably born c.?950. Her family held sway in western Normandy and Gunnora herself was said to be very wealthy. Her marriage to Richard I was of great political importance, both to her husband and her progeny. Her brother, Herfast de Crepon, was progenitor of a great Norman family. Her sisters and nieces married some of the most important nobles in Normandy.

Robert of Torigni recounts a story of how Richard met Gunnora. She was living with her sister Seinfreda, the wife of a local forester, when Richard, hunting nearby, heard of the beauty of the forester's wife. He is said to have ordered Seinfreda to come to his bed, but the lady substituted her unmarried sister, Gunnora. Richard, it is said, was pleased that by this subterfuge he had been saved from committing adultery and together they had three sons and three daughters. Unlike other territorial rulers, the Normans recognized marriage by cohabitation or more danico. But when Richard was prevented from nominating their son Robert to be Archbishop of Rouen, the two were married, "according to the Christian custom", making their children legitimate in the eyes of the church.

Gunnora attested ducal charters up into the 1020s, was skilled in languages and was said to have had an excellent memory. She was one of the most important sources of information on Norman history for Dudo of St. Quentin.As Richard's widow she is mentioned accompanying her sons on numerous occasions. That her husband depended on her is shown in the couple's charters where she is variously regent of Normandy, a mediator and judge, and in the typical role of a medieval aristocratic mother, an arbitrator between her husband and their oldest son Richard II.

Gunnora was a founder and supporter of Coutances Cathedral and laid its first stone. In one of her own charters after Richard's death she gave two alods to the abbey of Mont Saint-Michel, namely Britavilla and Domjean, given to her by her husband in dower, which she gave for the soul of her husband, and the weal of her own soul and that of her sons "count Richard, archbishop Robert, and others..." She also attested a charter, c.?1024?26, to that same abbey by her son, Richard II, shown as Gonnor matris comitis (mother of the count). Gunnora, both as wife and countess, was able to use her influence to see her kin favored, and several of the most prominent Anglo-Norman families on both sides of the English Channel are descended from her, her sisters and nieces. Gunnora died c.?1031 (wikipedia)