If you Really think option 2 is out, man up and tell that to her face. You clearly don't think that the two of you are dedicated enough, so it isn't going to work out anyway. The very fact that you don't think it could work out says you shouldn't even be together now because you aren't committed (or you simply don't trust her enough).

The only exception to the "you shouldn't be together now" is if you two haven't been dating for long. In that case, it's sane to say that it might not work out since you don't really know her and/or you haven't had time to decide if you're committed.

But even then I'd say ti shows a clear lack of interest on your part. This isn't to demonize you in any way, because you may gain said commitment later on after continuing to go out with her, but at this point if she's going away and that's how you feel, you shouldn't drag it out at all.