Nothing ventured, nothing gained.
Not every relationship needs to be about forever.
Currently, she has chosen you. Most women will have been someone's girlfriend at some point, so in this case you just happen to know about it.
So accept the facts as they are, be her friend, enjoy each other, hang out and hookup.
Maybe you get lucky, maybe you join the broken hearts club, but n this game you have to play or live alone forever. Not a bad choice in my opinion.