SP
I stand by my original post but would like to add one point.
How close is the girl you are dating to her parents?
There must be some distance since she is frum and they are not. But if she is very close to them, you need to assume worst case scenerio and plan from there. If they will basically stop talking to her, no matter what you will always be the reason for that.
If they aren’t close, than why worry about it?
If they were frum I would tell you to give them a copy of Rav Shlomo Friefelds biography. There is a fantastic story in there about the length he went to, to show respect to a student of his, that spent time studying Native American culture. Who knows, maybe the book would have a positive impact on their view of yiddishkeit in general.
Hatzlocho!