What is the ruling on a woman's fasting that she vowed for a year before her marriage, and is her ritual bath (ghusl) from janabah valid after Fajr prayer, and is she permitted to do so in Ramadan?

One must fulfill a vow to fast for a year; otherwise, if unable, an expiation for breaking an oath is required. As for someone who is in a state of janabah (ritual impurity) when dawn breaks, their fast is valid, and nothing is due from them. Indeed, the Prophet, peace and blessings be upon him, would awaken in a state of janabah, then perform ghusl (ritual bath) and fast. However, it is not permissible for someone capable of performing ghusl to delay it until after sunrise, in order to avoid missing the prayer.