Mishnah 2 addresses the question of when a father is entitled to his daughter's kesubah in a case where he never actually received the kesubah money. The issue is whether the monetary right remains with the father or passes to the daughter herself.
The stage of betrothal:
"Erasah v'gershah, erasah v'nisarmelah - kesubasah shelo" - when the father gave his daughter in betrothal alone, meaning that kiddushin were performed but not nisu'in, and she still lives in her father's home, and afterward the husband divorced her or died and she was left a widow - the kesubah belongs to the father. At this stage the rights to his daughter's money are still in his hands, since she is still a na'arah.
The stage of marriage:
"Hisi'ah v'gershah, hisi'ah v'nisarmelah - kesubasah shelah" - when the father married her off in full nisu'in and she began living with her husband, and afterward he divorced her or she was widowed - the kesubah belongs to her. Once the nisu'in took place the daughter left her father's domain, he no longer has any monetary control over her, and the money is hers.
The view of Rabbi Yehudah:
"Rabbi Yehudah omer: harishonah shelo" - Rabbi Yehudah draws a distinction and rules that the collection of the kesubah from the first marriage, which took place while she was still a na'arah, belongs to the father even though she was fully married. The reason: the kesubah was written before the marriage actually took place, at a time when the daughter was still in her father's domain and under his control. According to Rabbi Yehudah, the determination of who is entitled to collect the kesubah is not made according to the situation afterward, but according to the situation at the time the kesubah was written.
The reason he used the term "the first" is that with regard to any subsequent marriage it is self-evident that the daughter already left her father's domain from the moment she was married, and therefore the later marriage, including the writing of its kesubah, takes place while she is in her own domain and under her own control.
The response of the Sages:
"Amru lo: mishehisi'ah, ein lo reshus bah" - the Sages disagree with Rabbi Yehudah and hold that once she was married the father's control over her lapsed, and the kesubah money belongs to her. In their view the determination does not rest on the time the kesubah was written, but on the time of collection: at the time of collection the woman already stands in her own domain, and therefore the kesubah money goes to her.
In summary: at betrothal - the kesubah goes to the father, since the daughter is still in his domain. At marriage - the kesubah goes to the daughter, since she has left her father's domain. Rabbi Yehudah draws a distinction and holds that the kesubah of the first marriage belongs to the father, because it was written while she was still in his domain, and the Sages disagree and rule that the determination is made according to the time of collection, and once he married her off the father no longer has any authority over her.