Is what the wife said, "Our guest, and leave us," considered a prayer of polytheism (shirk)?

If a woman, in her jest, intends to address the electricity for its outage, there is no harm in that, because it is a metaphorical address common in language and not a supplication (du'a). However, if she intends to accuse the homeowner of stinginess for cutting off the power, then this is ill-estimation which is prohibited. What your wife said does not fall under shirk, and it is advised to abandon obsessive doubts and extremism in this matter.