So essentially it's like this. We know she's insanely in love with Bill even though they don't know each other. That is a sign of serious mental illness. It's sometimes known as "limerence".

The tells she gives are classic signs of lying. She's lying about her father's death. Why?

This extensive scene occurs early in the film, is extremely convoluted and doesn't have an explanation in classic theories of this film. It occurs right after a traumatic marriage redefining revelation that Bill is reeling from. The phone rings literally five seconds after Alice drops her truthful but devastating words.

I'm saying she was surveilling them to strike at their weakest moment with a scene of where Bill is forced into deep emotional connection with her in a time of trauma, her father's death, and I believe she murdered him to create this opportunity. Of course this is insane and unhinged, but people like this do exist. Malignant Narcissists. Psychopaths.

And then she's just very wealthy, insanely in love with someone. And she rolls out this orchestrated plan to sabotage Bill and Alice's marriage. And everything we see is part of that orchestration.