Even being online, it has to be a real relationship. If she goes off and gets with some guy, she cheated on you, and you need to just leave her. My longest relationship of 3 years 4 months (I'm 19) was online, and we did get together in person when he could visit. Cancer was the only thing that tore us apart. I was 12-15.
Tim, who I am with now, I also met online. Which is why I'm in Texas and not in Cali where I am originally from. We've been together for almost 2 years, from the day we met in person, and have known each other for about 5 years. He's now my fiancee.

If you both don't treat an online relationship like how it would be in real life, it's not going to work and you just need to move on to someone who's not going to cheat on you.