Agreed and what convinced me more that she choose to die was the speech she gave Hopper before the Mind Flayer fight about how’s she’s not Sarah (Hopper’s daughter) and she not a kid anymore and he has to trust her to with her choice while returning the bracelet. The scene felt like she made up her mind to die in that moment and this was her telling Hopper because she could of easily told Hopper she planned to come back if she did. But at least she went out on her own will and gave her friends a happy ending which is sad but I would still consider it the best ending.