What is the ruling on fasting last Ramadan before seeing menstruation for someone who has reached 15 years of age, taking into consideration that the age of puberty according to the Malikis is 18 years?

The answer clarifies the signs of puberty and the obligation of fasting. If a girl menstruates before the age of fifteen, she is considered to have reached puberty by consensus, and she must make up for the fasts she missed after reaching puberty through menstruation. However, if she menstruates after the age of fifteen and missed days of fasting after reaching this age and before menstruation, assuming she had not yet reached puberty, she is obligated to make them up according to the majority of scholars, and this is the more cautious approach. If she doubts whether puberty has occurred, the default assumption is that it has not, and thus she is not required to make up the fasts. If she is certain that she broke her fast after reaching the age of fifteen and before menstruation, she must make them up according to the majority of scholars. It is permissible to follow the opinion of those who rule that puberty is attained at the age of eighteen, as the layperson follows the reliable opinions of scholars.