What I would believe as a juror, since as you say it is weird... is that this happened in the recent pass just as she described but that at the last second she was able to point the knife away as a natural reflex.
Later, after giving it much thought she realized she could have killed her husband and then basically recreated the scene enough to kill him.
Especially given their history of police being called seven times because of loud arguments.
... but that at the last second she was able to point the knife away as a natural reflex.or was a foot short.