There's no one right answer to this question. Every girl develops at her own pace, and what feels right for one might not be right for another. It's more important to focus on healthy development and emotional maturity than age alone.
While some girls may start dating in their early teens, others may not be interested until their late teens or even early twenties. Factors like personal values, cultural norms, and individual maturity levels all play a role.
Ultimately, it's best to let each girl decide when she's ready for a romantic relationship. Open communication and guidance from parents and trusted adults can help her make healthy decisions.