How can a Muslim girl atone for not performing the obligatory Udhiyah (sacrifice) in past years?

Scholars have differed regarding the ruling on Udhiyah (sacrifice), whether it is obligatory (wajib) or a confirmed Sunnah. The most preponderant opinion is that it is a confirmed Sunnah for those who are able to perform it. Whoever does not sacrifice while being able to, does not incur sin, nor is he required to make up for past years, unless he had vowed to perform the sacrifice, in which case he must fulfill his vow. A Muslim should prepare his sacrifice before the advent of Eid al-Adha.