Yevamot, Chapter Thirteen, Mishnah Five
This mishnah continues to deal with the remarriage of a girl who has made a declaration of refusal.
If a minor made a declaration of refusal against a man, and then she was married to another man who divorced her, and afterwards to another man against whom she made a declaration of refusal, and then to another man who divorced her: she is forbidden to return to any man from whom she was separated by a get, but is permitted to return to any man from whom she was separated by her declaration of refusal.
In the scenario in this mishnah, a minor is married to a series of men, while she is still a minor. Against the first she makes a declaration of refusal, by the second she is divorced, against the third she makes another declaration of refusal and by the fourth she is divorced. She may now remarry the first or third since their marriage ended by declaration of refusal, and although she was remarried in the interim, since the original marriage ended with refusal it is as if it never existed. She cannot remarry the second and fourth husbands, by whom she was divorced, because she was married in the interim. Although the subsequent marriage was annulled and therefore should be treated as if it never happened, our mishnah teaches that it is still sufficient to prevent her from remarrying.