She's your "Girl Friend" or someone taking up space in your space ? 
Years ago, I took care of my Girl Friend - she didn't or rarely contributed monetarily . . . .  If she were simply another "guy" using your space, yes, split stuff up. If she's your "Girl Friend", I'd think you'd simply take care of her and she'll contribute in other ways (not sex either) to the success and future growth of you both.

As I said, I'm old . . . . . .  and old fashioned.