Did Elsa actually died in Jojo Rabbit?

In the end of Jojo Rabbit, we see Jojo lying to Elsa that Germany has won the war which leaves her in despair, and when he recites another made-up letter from Nathan, where he says that they both have figured out to get her to Paris, it took her a very long time to respond. Basically Taika Waititi wanted us to have a "heart in your mouth" moment where we think that Elsa committed suicide hearing that the Germans have won.... which she didn't, or maybe she did?

You see, the whole movie isn't from Jojo's perspective, but considering that the boy hallucinates Adolf Hitler as his friend, we can't be sure which of his scenes are real, and which are a figment of his imagination.

Like when the first time Jojo meets Elsa, we aren't sure if she's real or his imagination. Her appearance was very much like a ghost, the director wants us to keep us guessing and we aren't sure of her being real until we see Rosie interacting with her.....and even if she's real, that doesn't mean all the individual scenes of her and Jojo were exactly like it was shown. Because we are seeing her from Jojo's perspective. So she seems like a ghost at the first meet, dangerous at the beginning but as Jojo gets to know her more, we see her as a normal person with feelings.

The last single shot of Elsa in the movie was her in the attic when she hears the lie from Jojo about Germany winning the war. Then, after creating tension for a few seconds of whether she's dead or alive, the director shows her opening the door directly interacting with Jojo, telling him that her fiance died of tuberculosis one year ago, which sounds too good to be true.

If he was dead, why they previously showed Elsa getting sad when Jojo told her that her fiance broke up with her? He even gets scared that she might commit suicide. Was that foreshadowing? Of course, it's completely possible that as Elsa knows that Jojo is a liar, she's not stupid to completely believe him and take her life. Or maybe, Elsa does believe anything easily, and she did commit suicide and her dead body was inside the attic, while the one who came out and talked to Jojo was just his imagination.

That's why she said what he wanted to hear. As her fiance is dead he thinks she'll not leave her, and also in the last scenes, we don't see her interacting with anyone other than Jojo (the boy who hallucinates).

Maybe her boyfriend was indeed dead and she was just using it as a bait to prolong his talks with jojo . 

I believe other than his scenes with hitler which was him hallucinating , everything else does happens in real 

More than "hallucinations" its actually how kids make up a "friend" for themself. Like in Jojo's mind, Hitler eats the most random things and is almost child like (because the only adult figure Jojo knows is his mom) and when he "breaks off" this "friendship", for me, he stops making "friends" in his head and starts looking out for real people, real humans.

So no, Elsa is very much alive and very much has the last dance with him.

Elsa, wanting to have a bit of fun, may have end up Nathan, or he might be real and have died. Elsa didnt really have anything to go on in life, expect Jojo's mom, ad after her death, it was Jojo she thought of as a friend, a companion, her only family. So she might have continued the charade of being engaged just to make Jojo feel that its not like with him, her world ends (even if it does)

Your insights are actually good, but I think after his mother's death, Jojo stops believing in hitler and that's where he realizes how much Elsa has suffered and starts looking out for her, like his mother wanted and then dances with her, like his mother wanted.