Shaykh Abdul-Muhsin Al-Abbaad was asked:
Is using henna specifically for married women? Is this correct?
“This is not correct as is well known. No doubt women who are married have a need to beautify themselves for their husbands and there is no harm in training the young girls to wear henna. It is not a condition that beautification is only for husbands. Rather a woman can beautify using henna and use henna even if she is not married as long as it does not lead to harm or fitnah. This is because this [henna] is from the affairs of the women”.
[Sharh Sunan Abi Dawood no. 468]
Faisal Ibn Abdul Qaadir Ibn Hassan