I think that it is important to compromise a bit. Maybe, you will decide not to have a tv in your house, but you can also watch tv shows on the internet, and most computers can have dvds put into them, so that way, you can still get all the benefits of a television (although I am against watching tv myself, I don’t want a TV in my house, or secular literature outside of what my kids are stuck reading for school. The only barriers for me between where I am and where i want to be is internet usage, lack of background, and fact that I don’t like it when people tell me what to do). But as a baal teshuva, I can assure you that there are always ways to compromise with people without being so sheltered or feeling like your children do not know about the outside world.
It seems like the girl you are going out with is really growth oriented, and she probably wants to marry someone who is also really growth oriented as well. I think that the bottom line is that as long as you are willing to grow hashkafically along with her, that you both will be happy. It was very hard for me to stop watching tv as well, and stop reading teen vogue, and other magazines like that, so I started limiting the tv shows I was watching one by one, and I realized that I felt so much better about myself and felt holier each time I eliminated a tv show.