Imagine some new girl starting with the avengers as the same job role reader did, but she's on maternity leave as she's just had her and Bucky's first baby. This new girl has a massive crush on Bucky and flirts with him. One day reader brings Lottie and the baby to see everyone and when alone the new girl says something like "why are you parading Lottie around like she's yours when she's not" and says things that are untrue about Bucky, making out he flirts with her etc. And Bucky overhears the whole thing... his reaction? 👀👀👀