When a sacred family heirloom goes missing, a devoted widow is stalked by a deranged young woman who believes that she took the emblem and she viciously sets out to retrieve what might be rightfully hers.

Agree with Han_Heya.

There’s a lot of “she” and “her” in here. It’s quite difficult to follow who’s doing what.

If the widow is the protagonist, write it all from her perspective. If it’s the deranged young woman, from hers. If the deranged young woman is the protagonist, I struggle to see how an audience is going to connect with a deranged woman who viciously goes after things. If the devoted widow is the protagonist… well I have no idea of what the set up for her is other than she is a devoted widow.

Who owned the heirloom to begin with?

It’s a little muddled at the moment. I’m struggling to see connections between the elements. Currently, I feel I could simplify this as “When her heirloom goes missing, a crazy lady stalks the woman she thinks took it and tries to get it back”. ?Is that right?