What should a Muslim woman do regarding associating with Muslim women who openly commit sins after repeated advice, such as not wearing the proper hijab or going out with kohl?

Whoever sits with people engaged in sins, it is not permissible for him to sit with them as long as they are committing these sins, unless he can remove the evil by offering advice. Otherwise, it is obligatory for him to leave the gathering. Allah Almighty says: (And He has already revealed to you in the Book that when you hear the verses of Allah being denied and ridiculed, then do not sit with them until they enter into another conversation. Indeed, you would then be like them.) [An-Nisa 4:140]. However, if the person is not actively engaged in sin, then it is permissible to sit with him.

If the sister is secure from deviance and sees that there is a benefit in her companionship with them through advice and guidance, then her continuation in that is better. However, if she fears that they might influence her, then she must abandon sitting with them to protect her religion, especially if she has advised them and they have not responded.