Nora Allen (Earth-Prime)

"Here's what's really funny... Killing your mother led to the birth of the Flash, and killing Iris led to the rebirth of me. So, I guess you could say your mother... and Iris... were good for something."

- Eobard Thawne

Nora Allen was the mother of Barry Allen, better known as The Flash.

Death
In 2000, Nora was killed by Eobard Thawne during a battle between him and The Flash. The assassination caused a younger Barry to be a heroic vigilante in the future as The Flash after gaining his powers.

As the Speed Force
When Barry Allen started to communicate with the Speed Force, it used the appearance of Nora Allen to comfort Barry.