It seems more likely that Windemodis was the mother of Engelbert III, not the mother of Engelbert IV. I believe the mother of Engelbert IV, the wife of Engelbert III, was Mainfreda de Sens. Windemodis was probably born about 80 years before Engelbert III.
See
Engelbert II, comte de Brienne and relationships linked from there.
The wikipedia page for Engelbert III lists his wife as Windemodis and his mother as Mainfreda, but Windemodis was born CIR 900, and Mainfreda was born CIR 1000, so those relationships seem to be refersed.
https://fr.wikipedia.org/wiki/Engelbert_III_de_Brienne
I believe that Engelbert IV was the son of Engelbert III and Mainfreda de Sens.