Is a girl who has not been circumcised sinful, given the difficulty of doing so now, and how can she maintain her chastity if Allah has not facilitated marriage for her?

Circumcision for women is prescribed and is among the acts of fitra (primordial nature). Some scholars have held it to be obligatory, but the evidence for its obligation only supports its desirability. Therefore, there is no sin in not performing circumcision, especially when it involves hardship. As for ways for an unmarried woman to preserve her chastity, these include fasting, frequent remembrance of Allah (dhikr), reading the Quran, performing acts of obedience, abandoning sins, avoiding unlawful looking and listening, and associating with righteous people.