"I was at a point when I was like, 'I'm walking away from this business.'"
Marvel partnered with a Black woman-owned company for the collectibles.
The film is due in theaters this fall.
"Letitia kindly asks that you keep her in your prayers," said a representative for the actress.
Dorothy Steel, the 95-year-old actress who played a tribe leader in the first film, has also passed away.
The British-Ghanaian actress has joined the cast of the highly anticipated sequel, which recently began filming in Atlanta.
The actress's role as general of Wakanda's Dora Milaje will continue in the Marvel Cinematic Universe.