Headscratchers / Poirot

• The adaptation of Lord Edgware Dies has a moment not present in the original novel: after happily telling Poirot she intends to go out to dinner after all, Jane suggests he come with her, and he declines. In the next scene, he tells Hastings that the reason he declined is that he wants to host a small dinner of his own. Given that his acceptance of Jane's invitation to accompany her would have ruined her plan to murder her husband that night, and she couldn't possibly have known that he already had plans to host his own dinner party since he hadn't yet told anyone at all, why did she take the unnecessary risk of derailing her own carefully-prepared murder plan by inviting Poirot?
  • The lady is somewhat impulsive and flighty, so it could be simply a case of Did Not Think This Through. It could also have just been an invitation offered out of politeness and decorum, not intended to be accepted (and she may have breathed a sigh of relief when he didn't). It could also have been an overconfident variation of the Detective Patsy; she wouldn't be the first murderer to decide that her plan was more foolproof than it was and to try to throw any potential investigators off her tracks by brazenly "hiring" them (or, in this case, asking them to be present) in a way that suggested her innocence.