Does a woman who cuts off a colleague sin, given that she knows of her colleague's bad character and that many others avoid her?

It is forbidden to abandon a Muslim for more than three days, unless there is a legitimate reason. Scholars have permitted abandoning someone for more than three days if speaking to them would lead to a deficiency in religious commitment or harm to one's self or worldly affairs. Therefore, there is no sin upon you for shunning the aforementioned colleague. However, it is better to advise her and forgive her, and to avoid resuming your friendship with her if you fear an adverse effect on your religious commitment.