I think my own thoughts on Ilsa in dead reckoning is that narratively it is the most fitting end for her specifically.
This is mostly based on the fact that her entire arc has been centered around her ever growing desire to be free and acceptance that she cannot go back to her life from before.
She says to Ethan quite bluntly in Fallout “We are never free.” She says this to Ethan who knows better, who knows more than anyone that despite how hard he tries he will always be a field agent.
They’ve a fundamental understanding in this regard. Ilsa has spent her time in canon running from all sides, and taking care of her own self interest (which can align with Ethan’s interests but not always)
In dead reckoning when Ethan asks her when she was going to explain her connection to the key and Gabriel she says “I’m telling you now.” In Rogue Nation she doesn’t lie (the only time she does is to protect Ethan and Benji) she omits information and that is a consistent core of her character. As well as in Fallout, she doesn’t directly tell Ethan why he shouldn’t meet The White Widow.
All of this is to say that she’s been always caught between the world view of different men/government agencies and has never fully committed to any of those ideas. She understood both Lane and Ethan’s ideals while working under Atlee and rejects all of them in favor of being free of the system.
The ultimate tragedy is that she was right, she was never free. But she dies as a result of a decision she makes to stay rather than run. It wasn’t because her hand was forced or under someone else’s orders. She made the decision to go to that bridge knowing the risks (much like the rest of Team Hunt helping Ethan in spite of the risks)(hello boat scene from rogue nation)
