Nedarim, Chapter Ten, Mishnah Five
In Mishnah Ketubot 5:2 we learned that a girl who was betrothed and then reached majority age has 12 months during which she prepares herself for marriage. During this time he prepares himself and the wedding as well. A widow or a divorcee receives thirty days. If the betrothed husband does not marry her within this time, she receives her maintenance (cost of food) from him. In our mishnah, the Sages debate whether the husband also has the ability to annul her vows during this period.
[In the case of] a girl who has reached majority age who waited twelve months, or a widow [who waited] thirty days,
Rabbi Eliezer says: since her [betrothed] husband is responsible for her maintenance, he may annul [her vows].
But the Sages say: the husband cannot annul [her vows] until she enters into his domain.
Rabbi Eliezer holds that since he is responsible for her maintenance, in other words has financial responsibility for his betrothed wifes well-being, he receives the right to annul her vows. In contrast, the Sages do not give him this right until she actually enters his domain. According to the Sages he should have married her after this time period had elapsed. Therefore, while he is penalized and liable to pay for her maintenance, he does not receive the right to annul her vows as would a full husband.