...and a kidnapping in her hometown informed her character.

https://www.yahoo.com/entertainment/tv/article/winona-ryder-didnt-take-the-stranger-things-plot-lightly-how-otherworldly-grief-and-a-kidnapping-in-her-hometown-informed-her-character-214234407.html

When it came time to bring Joyce to life, Ryder didn’t need to look far for inspiration — she knew a family that experienced a similar loss.