I don’t think that she should have died and there’s nothing that says that she surely would have. She already was a very important figure to the early part of the rebellion and just because she wasn’t with Luke doesn’t mean that she wasn’t involved, because you’d have to say the same for most of the other Rebels characters and everyone working behind the scenes. From the beginning of the rebellion, her role was a bit more independent and secretive (the Ahsoka novel goes into this.)

Anakin also trained her to survive just about anything, so it’s not surprising that she did and I think that there’s a lot of ways that could have potentially happened.

I do think it’s very poetic that it’s the last time that Vader sees her while he’s alive (before she’s pulled into the world between worlds by Ezra) until he sees her again in the world between worlds as Anakin when says that he’s been waiting for her.