How does Leia die?

So far Luke, Leia and Han are alive. The bigger characters we have 로스트 are

Padme Amidala ( Mother of Luke and Leia)
Anakin Skywalker ( Father of Luke and Leia/ aka Vader)
Obi-Wan Kenobi ( Vader/Anakin's Jedi Master)
Jacen Solo ( Han and Leia's Oldest son/ Jaina's Twin)
Anakin Solo ( Han and Leia's youngest child and son)
Chewbacca ( Han Solo's Best Friend/ Brother figure)

Both of Han and Leia's son's are dead, their Daughter Jaina remains alive with them. Luke and Mara's son Ben Skywalker is still alive as well.

I saw somewhere that Vader used a syringe in episode 4 on Leia so she would die in a few 초 and then come back and tell the things she had kept secret. So she was dead for a while. The injection is in the picture.