When her mother dies suddenly and tragically, a distraught daughter must contend with her spiralling grief; but when the cult she has sought support from begins to take over her life, he must she must free herself and her family from their grip before they fall victim to a violent sacrificial ritual.

Deconstructing the logline, I get:

Inciting incident = mother dies suddenly & tragically

protagonist = distraught daughter suffering grief

antagonist = cult of violent sacrificial ritual.

A mother dying suddenly has a wonderful fairytale quality to it (although genre is Thriller). In my view, Grief is not a character trait - it's an emotion, felt by said character. An example of a character trait might be Withdrawn - which is then the outcome of grief and sadness.

Think how the logline might personify the villain? Currently the cult feels very anonymous, vague, difficult to imagine.