While it's great that you care for your friend like you do, I feel it's important to add that not everybody is required to be comfortable with sexuality. We live in a very sex-positive culture, which is totally cool. But we must remember that if someone finds that sexuality just isn't their thing, that's just as acceptable.

Have an honest talk with your friend, if that kind of talk isn't too awkward or intrusive (you be the judge.) It could very well be that your intuition is correct and she just needs a friendly reminder that this kind of stuff is natural and inevitable. Or she could just not be ready or comfortable with this being a part of who she is just yet, which is entirely her choice to make.