I want to ask my wife to shower when she starts to smell like sour breast milk.
Has she always smelt this way?
No, it just started happening recently.
While it is rude to describe your wife as smelling like sour breast milk, it is understandable that you are off put by your wife's body odor. When you live in close proximity to someone, such as spouses in a marriage, it is expected that you engage in good personal hygiene to prevent offensive smells from affecting your partner. You should try to tactfully discuss the issue with your wife and stress the importance of keeping clean so that she does not contract any health issues with her skin.
I'd rather use the school paper to brag about my wife than be helpful.
That is not very kind. You should find a way to bring this up in a kind manor. She might not know that she smells and would want engage in better hygiene practices to prevent it in the future.