פירוש על קידושין 7:2

The problem is that the comparison between the two “going outs” is not precise. When the maidservant goes free, she becomes completely free. Her master retains no control. But betrothal is only a partial transfer of authority. Her father still retains some authority over her and will continue to do so until she enters the huppah. So how can the two be compared?

The answer is that in one respect, even though still living in her father’s house, the father has lost control over her at betrothal—he no longer has the right to unilaterally annul her vows. Once betrothed, the father and husband jointly annul her vows.