The 616 Natasha and Shepard got along well, with an effortlessness that was a little bit scary when you remember the relative deadliness of the two women in question. I would describe their relationship as "bros". Possibly even with a rhyming couplet.

So I don't anticipate MCU Nat and Shep having too much trouble meshing in a positive fashion. Did you have anything particular in mind?

Also, Shep maintains that she would have whupped bucky's ass if not for the torture injuries and stuff. Whether or not that is true remains to be seen.