All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
We ask Allaah to reward you the best for your great concern to call your friend towards Islam and to fulfill the duty of enjoining good and forbidding evil. In fact, this is a characteristic of a believing woman. Allaah Says (what means): {The believing men and believing women are allies of one another. They enjoin what is right and forbid what is wrong.}[Quran 9:71], may Allaah increase your eagerness to spread virtuousness.
There is no doubt that giving good advice to a Muslim is a part of belief. The Prophet said: “The (essence of) religion is (offering) advice." If a Muslim sees another Muslim doing something which may harm him in this life or the Hereafter, he has to advise him wisely and sincerely. If he accepts the advice then this is what is required; otherwise, the adviser has fulfilled his duty and becomes acquitted from sin. However, the adviser should not abstain from advising his brother as long as he expects that he will benefit from his advice and will not harm him. Therefore, you should deal with your friend on this basis. For details see Fatwa 84348.
As for other friends, in principle, advising them is compulsory. Not receiving your advice or deeming that what they practice is correct, is not a religious impediment that prevents you from forbidding them from their evil acts unless you fear that forbidding them may lead to a greater evil. In this case, it is better to abstain from forbidding them from their evil acts.
A believing woman should not befriend such young ladies, because it is dangerous for her religion. The Prophet said: "Do not keep company except with a believer, and only a pious person should eat your food."
Allaah Knows best.