You can't legally get your GF to embrace sh!t. You can express you'd like it or ask her if she's ok with it, but if she isn't then you just have to accept that. Which leaves you with 2 choices unless she's disgusted that you'd want it and leaves, that is to stay with her knowing it's not gonna happen or leave her to make it happen.
It's a risk no matter how you twist and turn the issue. I doubt any answer here will satisfy you, because there's no guaranteed way to make it happen.