What is the ruling on applying cosmetics to a young girl who has not yet reached puberty?

There is no harm in adorning young girls. This is indicated by the fact that the Prophet, peace and blessings be upon him, gifted jewelry to Umama, his granddaughter. Similarly, Aisha, may Allah be pleased with her, used to adorn the orphaned daughters of her sisters, and no zakat was due on their jewelry. Strictness in preventing a girl from adornment might have adverse effects. If a girl is raised upon goodness, she will, by Allah's permission, be safe from committing forbidden acts after puberty. Moreover, this matter is too trivial to be a cause of dispute between spouses.