Is the questioner sinful for cutting ties with a truthful friend who caused her problems, knowing that she advised her many times?

The fundamental principle is that a Muslim should maintain ties with their brethren and cooperate with them in righteousness and piety. The Muslim who mixes with people and endures their harm is better than one who does not mix with them.

Therefore, if you can maintain contact with your colleague and invite her to goodness and to abandon bad manners, then continue your relationship with her. This is based on the Prophet, peace and blessings be upon him, saying: "For Allah to guide one man through you is better for you than red camels."

However, if you fear that she might influence you or harm you in your religion or worldly affairs, then distance yourself from her and abandon her in a graceful manner, by returning her greetings but not engaging with her. Scholars have unanimously agreed on the permissibility of abandoning someone for more than three days if one fears harm to their religion or worldly life from speaking to them.