Yes, no matter if it was years later and everyone was happily married with kids and grandkids, I would want to know how she died. If she had such a significant effect on your life, why not ask a few people some questions?
I don't think it's being a voyeaur. At her young age, it is not typical, and she leaves behind a daughter and a husband.
Don't you have some old mutual friends that you could ask?
Just tell them you have found this out recently and you are saddened to learn of her passing.
Also, I think anyone would have different reactions to death by car accident, terminal disease, robbery victim, or suicide.