If my 9-year-old sister ate during the day in Ramadan due to feeling hungry, what is the ruling regarding making up for that broken fast? Is it necessary for her to repeat it or should she observe two consecutive months of fasting instead?
Bismihi ta'ala
The age of taklif for a female is completion of nine lunar years, which in Gregorian calendar is 8 years, 8 months and 20 days (approximately).
If she is younger than this, she does not need to make up to anything, and her fasting is just for learning. If she is of taklif age, and she was extremely hungry, unable to continue fasting, she just makes up this day later on as qadha`, and there is no kaffarah.
It is always strongly recommended to wake up for suhur (pre-dawn) time and have a healthy meal, drink water, etc., to be able to avoid severe hunger during the day, especially for younger people.
And Allah knows best.