Love /
Polish girlfriends family, they want me to become Catholic. [20]
I was in the same situation a few months ago, but not because of religion but because of Nationality. My father and I had a massive fight because he didn't want to accept my relationship with my polish boyfriend and this carried on for months. To make a long sad story short, in the end, my father did accept our relationship, he even gave us his blessing to get engaged.
If your love for each other is strong enough, then you will be together no matter of others opinions or manipulative ways.
Also remember, like mentioned by others, that its her decision whether she decides to stick with you or give in to her family's demands. Just support her all the way!