If you want to join a dangerous mind control cult, the Jehovah's Witnesses, and give up having a decent wage for all your life because you will be discouraged from college or serious careers so that you can devote all your time to Watchtower, and if you think you can do this and remain pure around this girl- no sex and no french kissing sessions- until you are married at a young age (you will want to marry young because young people want sex so badly especially when they are truly in love and Jehovah's Witnesses will make sure you have only marriage sex), then maybe you can do all that for this girl.
The alternative is to cause her to violate the Jehovah's Witness rules and do something with you. Then she will hate you for causing her family and friends to shun her, and she will probably eventually leave you and try to go back to the Jehovah's Witnesses.
Romeo and Juliette is a great story about young love. Look up how poorly their story ended for them.
And when you try to dismiss adults who speak of your youth, your puppy love- remember that we were all there at one time. Most of us were in love at a young age and the vast majority of us know what you are feeling, and that you can get through your hormone-crazy youth without joining a cult.
If you really love this girl, tell her to be with her family until she is a young adult, then to come back to you. True love can wait 4 or 5 years.