To say she was concerned over her children - or to be more accurate, the various incarnations of her child - was putting it mildly. Sarah hadn't been one to let her son be independent since he was so breakable and vulnerable. She only truly trusted Bucky and still was becoming warm to Peggy Carter. It was nice that Steven was more confident but she was his mother first, second, last and always. She would always be protective.
She dusted down her best dress and knocked on his door with a box in her arms.