Nedarim 10:4, dealing with a case where a father has used his authority to marry off his 12-12.5 year old daughter through eirusin and is now finishing the marriage through nisuin, says:
דֶּרֶךְ תַּלְמִידֵי חֲכָמִים, עַד שֶׁלֹּא הָיְתָה בִתּוֹ יוֹצְאָה מֵאֶצְלוֹ, אוֹמֵר לָהּ, כָּל נְדָרִים שֶׁנָּדַרְתְּ בְּתוֹךְ בֵּיתִי, הֲרֵי הֵן מוּפָרִין. וְכֵן הַבַּעַל עַד שֶׁלֹּא תִכָּנֵס לִרְשׁוּתוֹ, אוֹמֵר לָהּ, כָּל נְדָרִים שֶׁנָּדַרְתְּ עַד שֶׁלֹּא תִכָּנְסִי לִרְשׁוּתִי, הֲרֵי הֵן מוּפָרִין, שֶׁמִּשֶּׁתִּכָּנֵס לִרְשׁוּתוֹ אֵינוֹ יָכוֹל לְהָפֵר:
It is the way of disciples of the sages, before the daughter of one of them departs from him, he says to her, "All the vows which you vowed in my house are annulled." Likewise the husband, before she enters into his domain would say to her, "All the vows which you vowed before you entered my domain are annulled," because once she enters into his domain he cannot annul them.
The exact case of the mishnah is not very relevant now, because girls don't get married at that age. However, a similar case is when a girl turns 12.5 and her father loses his authority to revoke her vows. He could say the same thing on the afternoon before her half birthday.
Does anyone recommend do that or do it in practice?