L.K.
The best thing you can do is refocus on something else and don't try too hard with them.
I remember being your daughter's age and I was the same way. I wanted NOTHING to do with my Mom. It took some time, but when I was about 22 my Mom and I became the best of friends. Especially if this is a serious relationship for her, she is embarking on very new feelings she has perhaps never had before and she may be doing things that she probably knows you might not approve of. It was hard for me to be close to my Mom or look her in the eye when I was in my first love/sexual relationship at a relatively young age.
Just keep your ears and door open to her and she will come back to you!