“What she has to do now will take all the rest of her strength” or whatever she says hardly clarifies much. It just says “Carrie Fischer’s character is about to go die.”
At least it clarifies that she’s making an active decision to do “something” vis a vis Ben, and that whatever it is requires the last of her power, similar to Luke’s final actions in The Last Jedi. Honestly, I’m not sure the visual storytelling here is strong enough to convey even that, as clunky as the line is.