[ה'תש"ל]
מגיל
שלום וברכה!
שש שנים או קודם מנהג נכון להדליק, כשהגיעה לחינוך (והבנה) בענין
זה
(ע"פ שו"ע אדה"ז סי' שמג ס"ג).
Shalom u'Vrachah!
Six years old or earlier is the proper custom to begin lighting, when she has reached the age of education (and understanding) in this matter (see Shulchan Aruch Admor Hazaken, section 343:3).
Summary
The Rebbe teaches that a young girl should start lighting candles at age six or even earlier, as soon as she is capable of understanding the mitzvah.