Gf’s lack of sex drive

Hey guys, so my girlfriend and I have been together a little over a year and a half. My pretty much only complaint is the lack of sex in our relationship. We have known for some time now that we both want to marry each other. This is the real deal. We’re happy and so in love. So why is the sex lacking? If it were up to me we’d be doing it every day. But unless I initiate something, she’s never in the mood. I want to be pursued, not always the one pursuing. We have amazing sex in my opinion and according to her as well. Do I just need to accept the fact that we might have sex only a couple times a month for the rest of our lives? I love sex, need sex. Thoughts?