Have I committed a sin by trying to straighten out my colleague who showed admiration for me, and does she have a right over me before God after she became angry with me and avoided me?

There is no harm in a woman loving her female friend, as this is a natural inclination, especially if the friend is a woman of religious commitment and good character. This love does not necessarily mean it is a passionate ( عشْق ) love, unless the love deviates from its natural framework.

If your friend has shown signs indicating that her love for you is not natural, then you did well by advising her. However, if she has not shown such signs, then you have harbored ill thoughts about her. Therefore, seek forgiveness from Allah and apologize to her.