In the real world, it is pretty obvious within the first 6 months whether you have a chance or not. All Elliot had to do was flirt some, invite her to things, etc. If she wasn't flirting back and coming up with excuses to not hangout with just him, then she's not interested. Girls will rarely say they're not interested, they'll just do what they consider to be nice and avoid the issue. He never had to directly confront her (big turnoff, girls like to play "the game"), all he had to do is indirectly check to see if she's interested.
Elliot should have moved on a long time ago...this plot is something that would happen in high school. Instead of worrying about someone who's leaving anyway, how about getting on with your life? If she says she doesn't feel the same way, his feelings are hurt. If she says she does, then he'll feel even worse when she leaves and mope endlessly. Chalk it all up as a failure and stop wasting your life being sad about this, there are plenty of other girls once you stop focusing on one that won't workout.