Good question. Haven't a clue as to who she is.
I suppose Yelena's "confession" at the end of 101 will open this story up a bit (I really liked that we saw how much fear and intimidation the Winter Soldier struck in his Russian peers.) I am enjoying the intrigue, but I go back and forth with Travel's art. Sometimes it's great, other times I think I am looking at Tom Cruise (Bucky) and some cartoon character (Clint.)