In “Captain Marvel”, Carol plays an incredibly important role in the young Monica’s life and constantly spends time with her and her mother Maria, acting almost like Monica’s unofficial second mother. At the end of the film, Carol sets off to explore the universe and help other creatures within it, and an excited Monica sees her fly into the night sky.
However, by the time “WandaVision” rolls around, the adult Monica is not cultivating Carol as she used to. In fact, she seems to have some anger towards her. When her SWORD colleagues Jimmy Woo (Randall Park) and Darcy Lewis (Kat Dennings) mention Captain Marvel in “WandaVision” episode 5, Monica abruptly changes the subject. Maybe she’s angry at Carol for essentially abandoning Rambeau’s when Maria presumably died of cancer alone.
That said, as the “WandaVision” finale mid-credits scene shows, a meeting between Monica and Carol arrives. During the scene, a SWORD agent (Selena Anduze) pulls Monica aside and reveals that she really is a Skrull sent to earth by “an old friend of your mother’s” who heard that she had been grounded. It sounds like Monica is on her way out into space, and when she knows she’s part of “The Marvels,” it becomes an intense reunion.