I just wanted to know if you had any advice to assist me in dealing with this particular situation. I have tried to approach my ex-girlfriend about allowing emotions to lead you to following false doctrine and learned that she has a new boyfriend, who apparently she believes is the ideal person because they can relate spiritually and that is one of the reasons we could not come to an agreement. It saddens me to see someone who bases all of her so called spiritual life on emotions and experiences as she is member of the one of the other denominations. I care for her and at times wish that she would open her eyes to the truth.
Yes, it is sad, but there is little you can do for her at the moment. If she has a new boyfriend, then she is caught up in the emotions of the moment. She will automatically reject anything you say negatively, thinking that you are just jealous. And besides, everything at this moment is perfect -- there are no flaws because he is perfect. Eventually the newness will wear off. Then she will be thinking more rationally. She will either discover she really does care for this man or she will move on to another to get another emotional high. But all of this is out of your control.
Remember that even the Master Teacher, Jesus Christ was unable to persuade all the Jews. He knew that their rejection of him would eventually lead to their destruction, but he was unable to talk them out of their destructive path. "O Jerusalem, Jerusalem, the one who kills the prophets and stones those who are sent to her! How often I wanted to gather your children together, as a hen gathers her chicks under her wings, but you were not willing! See! Your house is left to you desolate" (Matthew 23:37-38). If Jesus could not convince some, I think we must realize that there are many whom you and I will not be able to convince of the truth either.
It's is time to move on. There are people who are interested, if we can find them. Life is too short to spend a lot of time on those who are not interested. "If the household is worthy, let your peace come upon it. But if it is not worthy, let your peace return to you. And whoever will not receive you nor hear your words, when you depart from that house or city, shake off the dust from your feet" (Matthew 10:13-14).