Ordinarily, a married woman should defer to her husband to affix the mezuzot. But if this will cause an unnecessary delay, she should do it herself. A husband may choose to share the mitzvah with his wife, just as he may choose to share it with other persons of honor, such as a revered rabbi.
Incidentally, a mezuzah can be affixed at night.
 Sha’arei HaMezuzah 16:6:13.
 Bei’ur Halachah 135 cited in Agur B’ohalecha 17:39.
 Mezuzot Beitecha 289:3; Sha’arei HaMezuzah 16:15.