I fail to see how telling the pastor is edifying to anyone in the situation. This man is married. If he has feelings for this woman then God can convict him of it. However, her professing she has feelings toward him in a private discussion could very well plant seeds that don't need to be planted if their is mutual affection especially given the vulnerable state that this lady is in, whereas saying nothing and leaving keeps everyone's dignity and reputation in tact and prevents further instigation of something that would not be right any way.
If telling in some way practical benefits the pastor and/or his wife then fine but I can't see how it would. When would it ever be appropriate to disclose your attraction to a married man? I find that confession to that man is often just a way to test a hope that he will feel the same way and somehow find "permission" to commit the sin you've been thinking about anyway.
Assuming we all agree that Adultery in your heart is a sin.....
Matthew 5:27-28 “You have heard that it was said, ‘You shall not commit adultery. But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart."
James 5:16 Therefore confess your sins to each other and pray for each other so that you may be healed. The prayer of a righteous person is powerful and effective.
Prov 28:13 (NIV) He who conceals his sins does not prosper, but whoever confesses and renounces them finds mercy.
Acts 19:18 (NIV) Many of those who believed now came and openly confessed their evil deeds.
Mat 10:26-27 (NIV) "There is nothing concealed that will not be disclosed, or hidden that will not be made known. What I tell you in the dark, speak in the daylight; what is whispered in your ear, proclaim from the housetops."
Mark 4:22 (Jer) "For there is nothing hidden but it must be disclosed, nothing kept secret except to be brought to light."
Lev. 5:5 - "he shall confess that in which he has sinned"
Numb. 5:7 - "he shall confess his sins..., make restitution..."
Prov. 28:13 - "he who confesses and forsakes his transgressions will find compassion."
Acts 19:18 - "many kept coming and confessing and disclosing their practices."
I John 1:9 - "If we confess our sins, He is faithful and just to forgive us our sins."
Ps. 38:18 - "I confess my iniquity"
Some of you may argue that there's no need to confess your sins to the person of whom you have sinned against....but in order to be forgiven, the person has to know.
I don't believe confessing this sin of lust will plants seeds of sin, if this was the case, why would the bible stress confession. Wouldn't it say somewhere that "if we confess our sins of lust we will plant seeds of adultery"??