I am in a serious committed relationship (3+ years) and have never had a conflict between my g/f and my car. She knows how important my car is to me, and thats fine with her, and infact she claims to like the car too.
When we first started dating my g/f made a critical comment about my car. I simply pulled over and asked her if she would like to walk home. She said "no", and I told her than be happy your in a car.
Infact I have her so brainwashed she is now calling out Firebird models down to a year + or - before I do.