I keep thinking of THE WITCH THAT CAME FROM THE SEA... it's been many years though.......
It sounds interesting, but it isn't. I found an information that Rosagunde Renaldo (fl. 568) was the first princess of Genovia, so maybe it is good trope. "Rosagunde wore her hair in a long braid, which she used to strangle Alboin".
Perhaps it is fictional character, which is connected with other old legend.