yes,the halo thing means she was poisoned already when her friend saw her walking down the street so maybe she tasted it before cooking it? Not the dough surely. Or she nibbled a bit of the crust when it was done. Dunno if that would be enough poison. The scrubbing her nails thing, makes you think she is panicky about the poison but then if so, after cleaning her hands, why would she eat it? IF she knew she had eaten a poisoned pie, she'd try to vomit rather than scrub her hands.
Good point though, it's true if she didn't eat it, who did? Maybe a cat got at it? I think they cannoit solve it now , so Bates will die in prison and they can wrap it up