"This dress is owned by my little sister."

Translation: Gaun ini dimiliki oleh adik perempuanku.

[JudithAver]

I thought the perempuan was unnecessary. The dress is unlikely to be owned by a younger brother, but if it were, then the gender clarification would be appropriate.

[ChrisNeedh5]

Surely "Gaun ini dimiliki oleh adik perempuan saya" should be accepted? In fact, is it not more appropriate than the given answer, because 'adik' could refer to either a brother or sister?