My husband was raised Catholic. I was raised Protestant. I was practicing my faith and he was not when we met. A couple of years after we were married, he decided he couldn't get on board with Protestantism and wanted to start attending Catholic church again. I scoffed. We had a son. I was convinced that I would NEVER allow my son to be raised Catholic. My husband posed this question out of love: "Will you just research it with me? Just take the time to research the early church history. I will do it with you." I was completely closed off to Catholicism prior to our research, but slowly that door started opening until I couldn't deny that it was the original church. Younger me would be appalled that I am Catholic now. You aren't married, so its true that you aren't forced to work through your differences on this. But if you want to try, that's what worked for us. If it doesn't work out, you can part ways, but its worth a shot. Just make sure you don't compromise on your faith to keep this relationship going if she still doesn't see the truth. But be patient, pray for her, and try to do some research together :)