Nobody knew there was even a "MJ" in the movie until the last couple of minutes. That was not something they used to draw people into the movie. They flshed out her character fine, but she still wasn't MJ. She wasn't even a love interest. She wasn't an aspiring actress. She didn't have red hair.They bank on the name to attract people to Homecoming knowing her popularity
The ONLY thing that ties her to Mary Jane was the fact that she knew Peter Parker and she has the same initials. By that argument, Lex Luthor and Lois Lane are the same character.