Questions & Answers about Моя жена сама приготовила ужин.
Because моя has to agree with жена in gender, number, and case.
- жена is feminine
- singular
- nominative here, because it is the subject
So the correct form is моя.
Compare:
- мой муж = my husband
- моя жена = my wife
- моё письмо = my letter
- мои друзья = my friends
Because жена is the subject of the sentence — the person doing the action.
In Моя жена сама приготовила ужин, the wife is the one who prepared the dinner, so жена stays in the nominative.
A very common rule in Russian is:
- subject → usually nominative
- direct object → often accusative
So here:
- моя жена = subject
- ужин = direct object