What you are describing is a classic collision between the life of the Spirit and the self-life. The frustration you feel, that vexation of spirit, is a clear sign that something inside you is being pressed. It is easy to think the problem is entirely outside of you, in her obnoxious behavior, but the intensity of your reaction is also revealing something about the battle within. Your spirit is lusting against your flesh, and the flesh, that old self-rule, wants to assert itself. It wants to address her, to control the situation, to demand that she act in a way that pleases you. That is the self-life crying out for its own way, and it never leads to the calm you are seeking.
The supernatural work God wants to do here will likely come in a very natural, very difficult package: patience. And patience only takes root when we come to the end of our own resources. You have reached a point where you say, “I am having great difficulty removing myself.” That is a good and honest confession. It is the same cry as, “Who shall deliver me?” You have tried to ignore her, and you cannot. That is because the solution is not found in trying harder from your own strength. The path to calm is the path of self-denial. Before you worry about her behavior, bring your own frustration, your need to control, and your desire to address her, and put them on the cross. Acknowledge that the old self-governed life, which reacts in the flesh, was crucified with Christ, so that you are no longer a slave to that inner turmoil.
In this waiting, God is not being slow. He is working, and His patience is a model for us. Through the scriptures, we find comfort by seeing how long He waited with people, working out His purposes. He is waiting for a perfect fruit from this hard soil. Right now, the fruit He wants may not be a changed colleague, but a changed you, a spirit established in peace regardless of the storm around it. Discernment is indeed the hardest part: “Is this urge to speak from God, or is it my own justified frustration?” When the supernatural comes, it often comes with a quiet restraint, not with a fierce insistence. If you do not yet have a clear, calm, and loving word from the Spirit, then wait. Do not give God a deadline of Saturday. Do not be slothful in the waiting, but follow the example of those who through faith and patience inherited the promises.
Your hope is not that she will suddenly behave. Your hope is in the Lord Jesus Christ and in the certainty that He is in control of this entire situation, including your own heart. The God of all comfort will grant you to be like-minded toward her according to Christ, patient, as He is patient with you. The difficulty is beyond you, and that is the point. If the work were up to you, it would be impossible. But if God is the agent doing the work in your life, throw away the word “difficult.” You dare not trust in yourself. Go back to Him and drink. He alone fills that spiritual void, quieting the turmoil with His presence, and giving you the patience to wait for His work to be done in His time.