I think it could be fairly described as a 'Crime Passionel'.
A crime of passion, or crime passionnel, in popular usage, refers to a violent crime, especially murder, in which the perpetrator commits the act against someone because of sudden strong impulse such as sudden rage rather than as a premeditated crime.
Crime of passion - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Crime_of_passion
It certainly wasn't premeditated or 'first degree murder'. It makes little difference to the deceased or her family though.