少女, 乙女, 小女, しょうじょ, おとめ
1. little girl, maiden, young lady, female usually between 7 and 18 years old
Only 少女, Only しょうじょ, Archaism
2. female between 17 and 20 years old (ritsuryo period)
あのかわいい少女は私の妹です。
は
Particle, pronounced わ in modern Japanese
1. topic marker particle
2. indicates contrast with another option (stated or unstated)
3. adds emphasis