I think it's a connection to make in the proper time and place. I mean, I there's no real-world protocol for AU descendants, but it seems like springing that on them in the heat of battle is...not the smartest way to go. I think Natasha is generally overprotective of Bucky, and is probably harsher in general if she thinks she's somehow helping him. This isn't exactly a strong point, but I think it makes sense. I also think Bucky and Rikki actually meeting in that situation would wind up worse than the meet-up between her and Rikki. Better Rikki be angry at Natasha than angry at Bucky. Time will tell if she has any motivation, but she has a history of being really mean when she's actually trying to protect people. I mean, she shot Daredevil through the chest once. She also tried to scare the original Thunderbolts straight, and she didn't pull any punches, there.
The thing is though, that the Nomad identity also has a ton of issues that go with it, ones that the current Captain America is certainly fully aware of. I wonder if they'll reference that, as such a harsh story seems kind of outside the tone of the book. (Though the original had cartoony art, too.)