The medical examiner is the one who estimated her postmortem interval, dying likely in the late 50s. Other than the interval, there's nothing to indicate she couldn't have died EARLIER than the 50s. There's not much to go on, clue-wise. We have the neighborhood, her unique teeth overlap/pattern, the gold foil restoration dental work. Gold foil work began in the late 1800s and was phased out in the 1960s+, at least not taught in dental school beyond then.
I think it's entirely possible, or at least worth being open minded about, that she could have died long prior to the 50s. Gold foil restoration work was very expensive at the time, and again, it's stated that she had extensive work. Then why not also have braces? If you have money? To fix the front overlap and straighten out her teeth. Braces were around in the 20s-40s, more popularized after the 60s, but around nonetheless. But that could also be indicative of her age..I was super young when I had braces (put on at the end of 5th grade and removed middle of 7th grade), but I'd say that's not common. More so mid-later teen years, right? And if they were waiting until that age, then I think she's on the lower end of the age range, 14, 15, maybe 16. This is what I have running through my mind! Never-ending little avenues of thoughts.