Well Technically Hela is Immortal atleast in comics. And i dont think Hela died, As the entire planet exploded she might have just been frozen in space.

Most probably she did die.
But in comics, she is immortal so maybe she didn’t.
But she drew her powers from Asgard which had been destroyed, so even if alive she probably won’t be as strong as before.

She is not dead for sure because she is immortal and goddess of death herself. So there are less chances that she is dead.

Bela is immortal according to the comics and she would draw her powers from Asgard but as the Asgard is destroyed she could be some where in the universe like imprisoned or something like that.

In comics hela is an incarnation of the lady death which makes her immortal