So we all know that Natasha Romanoff is a widow red room bad ass right? So I was thinking that there’s two ways this can go depending on your writing style. One is completely platonic and so Person A, lets call her Alex because it’s easy to spell, and Nat (Natasha) are in the red room together and they become friends or they knew each other before the red room and stayed friends secretly through training. You may have to change Nat’s backstory a little bit to make it work.
Option two is that they fall in love and do lovey things and other lover stuff. This can both be friends to lovers or if you want a more enemies to lovers approach as have them be pitted against each other during training but on a mission together they make up and fall in love I guess? However you want to do that.
Anyways the idea is that Alex and Nat grow up on the red room go on missions but years layer once Nat has joined the avengers they have to pretend like they don’t know each other for whatever reason.
Few more options here, A) Nat and Alex get out together and join SHIELD and the avengers together. B) Nat does her whole story and Alex joins the avengers later and that’s when they meet. C) Alex is still stuck in red room/HYDRA and the avengers capture her and Nat recognizes her. D) create your own.
Personally I think C is the one with the most drama but I’m just the prompt giver you create what you want.