There seems to be a majority of sources that indicate that she was sister, not daughter of Fulk; and possibly, somehow, a niece of Gilbert Count of Brionne. I will stick with Turton, even though he is somewhat unreliable, because the other pedigrees don't seem very clear (and reliable) to me either.
Following is a post-em from Curt Hofemann giving, conflicting information on Gunnora:
First, it's Aunou, not Anjou . . .
Flwg are my notes:
parents: Gonnor (Gunnor) was the daughter of Baldric the Teuton, and a niece of Gilbert, Count of Brionne. [Ref: McBride2 citing Burke's p118-120, CP VI p498-503, Wurts p47-70], father: Baudri "the German", father of Nicholas de Bacqueville, Fulk de Aunou, Robert de Courcy, and Gunnor [Ref: TAF 21 Aug 2000 citing: Keats-Rohan "Domesday Book and the Malets: Patrimony and the Private Histories of Public Lives" in *Nottingham Medieval Studies* xli (1997), 18] Gunnora, sister of Fulk de Aunou is not daughter of Osmund, but of Baudri. [Ref: TAF 26 Aug 2000] Fulk d'Aunou had a sister Gunnor [Ref: TAF: 21 Aug 2000]
Research note 1: father Fulk son of Baldric [Ref: Turton]
Research note 2: Gilbert's wife Gonnor (Gunnor) was the daughter of Baldric the Teuton, and a niece of Gilbert, Count of Brionne. [Ref: McBride2 citing Burke's p118-120, CP VI p498-503, Wurts p47-70]
Research note 3: She (Elisabeth Van Houts) also argues that Robert confused things, that it was Baudri "the German", father of Nicholas de Bacqueville, Fulk de Aunou, Robert de Courcy, and Gunnor wife of Gilbert Crispin, who married the niece of Duchess Gunnor, while it was Nicholas's wife, Gertrude, who was niece of Gilbert of Brionne. [Ref: TAF 21 Aug 2000 citing: Keats-Rohan "Domesday Book and the Malets: Patrimony and the Private Histories of Public Lives" in *Nottingham Medieval Studies* xli (1997), 18] note: this implies the Fulk was Gunnora's brother, not father...Curt
Research note 4: First of all, while there is extensive debate, it is not generally fealt (sic) that Fulk d'Aunou, son of Baudri the German is the same as Fulk "de Alneio", son of Osmund of Centemvilliers. (For example, Wace appears to distinguish the two toponyms.) Thus Gunnora, sister of Fulk de Aunou is not daughter of Osmund, but of Baudri. Likewise Gunnora de Aunou married, not Gilbert de Brionne, but Gilbert Crispin. Gilbert de Brionne comes into play as supposed uncle of Baudri's wife, although this seems chronologically impossible... [Ref: TAF 26 Aug 2000]
Research note 5: ...based on the fact that Fulk d'Aunou had a sister Gunnor, Keats-Rohan has suggested that these two somehow got switched, and that it was Baldric who married the Gunnorid, while Nicholas married Gilbert's niece. This works better chronologically, since Gilbert de Brionne was two generations after Gunnor, his niece three and Nicholas four, while the wife of Nicholas would be just one, or perhaps two generation removed from Gunnor. Reversing them as Keats-Rohan suggests makes the wife four, and the husband three or four (because some of the nieces appear to have been grandnieces). [Ref: TAF: 21 Aug 2000]
Regards,
Curt