Complex sentence: She was 3 years old when her family discovered that she can sing as she was left alone with the karaoke machine, she sang the Regine Velasquez' song, "You are my Song".
Split into simpler sentences: She was 3 years old when her family discovered that she could sing. When she was left alone with the karaoke machine, she sang the Regine Velasquez' song, "You are my Song".