Nedarim, Chapter 10, Mishnah 3. Before we approach the Mishnah itself, one fundamental fact must be established, for without it the Mishnah cannot be understood: the difference between a husband and a betrothed man (arus) with regard to the power to annul vows.
The husband: Once the marriage has taken place - the second stage, which follows the betrothal - he can annul his wife's vows, but he cannot annul "b'kodmin", that is, vows that she made beforehand.
The arus: As long as only betrothal has taken place, he can annul even "b'kodmin" - even vows that preceded the betrothal, as our Mishnah teaches.
The words of the Mishnah:
"Nadrah v'hi arusah" - she made a vow while she was betrothed.
"Nisgarshah bo bayom" - she was divorced from him on that very same day.
"Nisarsah bo bayom" - and she became betrothed to another man on that very same day.
"Afilu l'meah" - and even to a hundred different men, theoretically.
"Aviha uva'alah ha'acharon mefirin nedareha" - her father and her last betrothed, even though he is the last of them all, annul her vows together, including the vows she made earlier during the previous betrothals. The reason, as stated, is that the arus, together with the father, annuls even b'kodmin.
"Zeh ha'klal":
The Mishnah concludes with a general rule: "Kol shelo yatz'ah lirshus atzmah sha'ah achas" - as long as the daughter has not come into her own domain even for a single hour, meaning that she has not left her father's domain entirely. Coming into her own domain happens in two ways: by becoming a bogeres (reaching full adulthood), or through marriage. And as long as she has not left, even if she became betrothed many times over - "aviha uva'alah ha'acharon mefirin nedareha": her father and her current betrothed annul her vows together.
In summary: In this Mishnah we learned the difference between a husband and an arus - that a husband does not annul b'kodmin, whereas an arus annuls even b'kodmin. From here we learn that a woman who made a vow while betrothed, was divorced, and became betrothed again on that same day, even to a hundred men, has her vows annulled by her father and her last betrothed. And this is the rule: as long as she has not come into her own domain even for a single hour - whether through adulthood or through marriage - her father and her last betrothed annul her vows.