Speculation was rife over which character Stranger Things actress Sadie Sink will be playing in the MCU. The next phase sees the emergence of mutants and the formation of the X-Men, so it was always assumed she would be one of them. Her character will make her first appearance in Spider-Man: Brand New Day.
One rumor that absolutely would not go away was that she would be this universe’s version of Phoenix / Jean Grey.

In the comics, Jean possesses psionic powers. Initially capable of using only telekinesis, she later developed the power of telepathy. During her early stint with the X-Men, she used the codename Marvel Girl.
Jean is a caring, nurturing figure, but she also has to deal with being an Omega-level mutant and the physical manifestation of the cosmic Phoenix Force. Jean first experienced a transformation into Phoenix in the X-Men storyline The Dark Phoenix Saga, arguably her most famous story arc.
Now, a report by The Hot Mic’s Jeff Sneider has said that she is definitely playing Jean Grey. This is apparently from the same, reliable source that has been right on a number of things, including the casting for Sam Mendes’ Beatles biopic.
There is no official announcement from Marvel Studios so far.
Two incarnations of Jean Grey have appeared in 20th Century Fox’s X-Men film series from 2000 to 2024. The first incarnation was portrayed by Famke Janssen. The second incarnation, a younger version of the character, is portrayed by Sophie Turner in the later X-Men prequel films.
Destin Daniel Cretton (Wonder Man, Shang-Chi and the Legend of the Ten Rings) directs Spider-Man: Brand New Day, which is due out in theaters this summer.