Be patient. You can have all the game in the world but if the girls not feeling it then there is nothing you can do. Be a gentlemen & not a whiney little twit that always begs for sex. That's just pathetic. Trust me, millions of other guys know how you're feeling. Everytime you see this girl you just want to rip off all her clothes and have "passionate sex" right? Been there, done that. Just be patient and be a gentlemen. It'll pay off once she's ready. Until then self pleasuring is your only option. Been there too and so have every other post pubescent guy that ever had sex. If they say they have never masturbated. They are so full of shit or they're virgins. That's as real as it gets!
Wait till you get married and it won't be a problem.
Relax and let time do somethings for you. Spend time with her alone
You don't. Pressuring someone into having sex with you makes you scum. Be a man for once and wait till she's ready or better yet until you've married her.
Engagement ring, marriage license, wedding, wedding ring in that order. Otherwise shut up until you can man up.