Pretty sure she *is* from the future. When she was introduced in DC Rebirth, she was arrested for stealing a sandwich. Her explanation was that where she comes from, food is free.
I imagine that hockey game murder does coincide with the history of this event somehow. Or it might be one of those details a historian might highlight to give a flavor of the times.
That said, whenever the Legion knows something in great detail about our era, I think about all I know of the day to day life in New Jersey in 1017. (Then again, as a time traveler, with possible access to time-viewing technology too, she'd likely be better informed on events she was heading back into.)
Johnny Thunder and/or the Thunderbolt has something to do with all this? Will this result in the return of the JSA? I gather that the Rebirth universe doesn't have any JSA connections(?) as Barry doesn't associate his vision of the Helmet of Mercury with Jay Garrick.
During the trip on the cosmic treadmill it was interesting to see the vignettes of the JLA. Barry says "that's not how the Justice League formed" when, as far as I'm concerned, it is. Is the one showing Zatanna supposed to be from the infamous Identity Crisis miniseries, which I successfully avoided?
Is the handgun in the case supposed to be the one that kills Martha and Bruce Wayne in Flashpoint?