sigrdrífa occurs both as a common noun, a synonym of valkyrja, and as a proper name of the valkyrie named Hild or Brynhild in the Prose Edda.
H. Reichert, "Sigrdrifa (Brynhildr)" in: McConnell et al. (eds.), The Nibelungen Tradition: An Encyclopedia, Routledge (2013), p. 119.
H. Reichert, "Zum Sigrdrífa-Brünhild-Problem" in: Mayrhofer et al. (eds.), Antiquitates Indogermanicae (FS Güntert), Innsbruck (1974), 251–265.
heimskringla.no
Finnur Jonsson (1932), De gamle Eddadigte, digitalized at heimskringla.org
