Monica Rambeau has been confirmed to be part of the Marvel Cinematic Universe, as daughter to Captain Marvel's Maria Rambeau, according to Entertainment Weekly. Whether or not she'll be mentioned on-screen or appear in the movie remains to be seen.
In an interview with Lashana Lynch, EW reports that her character Maria Rambeau is "also a single mother to a young daughter named Monica."
No actor has been announced for the Monica Rambeau role.
Monica Rambeau debuted in comics in 1982, and became the first female Captain Marvel - eventually leading the Avengers. Since then she's gone through several subsequent names, settling on 'Spectrum' and becoming an ally of the current Captain Marvel, Carol Danvers. In Captain Marvel, Monica's mother Maria has the nickname "Photon" - another superhero name Monica went by in comic books.
As for the MCU Monica, if she is a child in the mid-1990s Captain Marvel then she would be an adult in modern MCU times (such as say in Avengers 4 or other unannounced Marvel Studios films).
Lashana Lynch says that Black Panther is affecting how she is portraying the elder Rambeau in Captain Marvel.
"I, especially after watching Black Panther, want to keep the black community in a place where they trust that every single African-American character in the Marvel universe is going to be represented positively, is going to be represented accurately, and is going to have a real through-line that the black community or people of color will be proud of,” said Lynch.
“I want Maria to be upstanding,” the actor added. “I want her to have a voice, I want people to understand her and relate to her, and I want mothers to be proud that there’s a single mother in the MCU.”
Captain Marvel is due out in theaters March 8, 2019.