Reeling from the death of her beloved father and a difficult breakup, Monica, is ready to move forward with her life as she tries to land the new hosting job for an afternoon talk show. When she hires a new assistant, Simone, the two quickly become close friends as Simone moves in next door and completely immerses herself in Monica’s life. But underneath her sweet exterior, Simone harbors a dark secret and as time goes on cracks in her façade begin to appear. Monica decides to sever ties once and for all with Simone, but Simone has other plans and is determined to take over Monica’s life for good.
But there is an extremely uncomfortable moment where the antagonist watches the protagonist have sex and touches herself while watching. [SPOILERS] They're half-sisters.
The antagonist is portrayed as having abandonment issues and such, and a supporting character makes a condescending comment about her needing therapy. I'd say it's intended to show the antagonist as mentally ill and very, very violent.
For the 2022 movie, no animals were involved at all.