One of my good friends in high school was always having problems like this because he actively pursued relationships with a few of the girls in our class. I can tell you that none of those relationships worked out and just resulted in him getting frustrated and hurt. I stayed away from this stuff in high school simply because I didn't want the frustration. Believe me when I say that this stuff is much easier in college. I started a relationship with a girl the summer after my sophomore year in college and it was easy in comparison to this high school crap. I didn't try to actively go after her and give her gifts and crap to try to win her over - I tried to just be cool and collected and let things go as they might. We went out to dinner, went to movies, and simply just spent time around each other in class and after class (it helped that we were both chemistry majors, so we had similar schedules). Nothing more. We didn't spend our time trying to impress each other. Hell, for one of our first few dates, I took her to the redneck local dragway and dragraced my Camaro all night - she was/is by no means a car person, and she spent most of the night by herself sitting in the stands with the drunk rednecks. We just used our time together to focus on learning about each other and what made each of us tick. It worked out great. There was very little heartache, very few self-directed questions about whether or not I was doing the right thing for the relationship, etc. During this time, we naturally formed a very strong relationship without a whole hell of a lot of effort. The basis of our relationship has been strong enough to withstand living 10.5 hours apart from each other for the past 2 3/4 years while I attend medical school and she attends optometry school, seeing each other only a few times a year. I will have been with her for 5 years this coming June, and we have been engaged for 14 months now. Things just work better if the two people in the relationship are just their natural selves without all the extra crap you are dealing with. Period.
What I'm trying to say is that if it doesn't work out with her, don't sweat it. It's a high school romance, and from my personal experience, high school romances suck. Only in very rare cases are high school relationships built to last. My advice to you is to not worry so much about her, focus on your schoolwork, get into a good college, and just be yourself in college. Relationships seem to be much easier to handle and cultivate in college.