Zendaya was not playing Mary Jane Watson, just a character named MJ.
Everyone remotely familiar with Spider-Man lore knows that Mary Jane Watson, often known as MJ, is the love of Peter Parker’s life.
It was mostly surprising due to the fact that Marvel had furiously campaigned on the fact that Zendaya was not playing Mary Jane Watson; in a way, they weren’t lying.
Of course, the MJ they meant was the Mary Jane Watson, so we can say they weren’t lying on a technicality.