Is a female teacher sinful for not advising her female students who do not wear the hijab?

It is not permissible to teach in a place where adolescent or adult males mix with girls, especially if the girls do not adhere to the hijab, because this is an unlawful mixing. An adolescent is like an adult in ruling. However, if the teaching is for girls only, it is permissible, provided that enjoining good and forbidding evil is practiced, and they are commanded to wear the hijab and dress modestly, with the intention of reform. This is because the presence of righteous people in places of disobedience, while advising its inhabitants, achieves a great benefit in reforming society.