What this guy said! I also started quite late didn't have my first kiss/relationship until I was 18 and have gotten to be successful with women over the years. Don't sweat it or internalize it, your time will come. Work on the flirting, this is very helpful in building attraction.
Maybe she's just a bit on the dumb side and you just need to keep doing what you're doing, maybe she's nervous and you are taking her reaction as a rejection whereas you just need to keep at it
