I don't think any of these paths are going to happen, though the third seems possible enough.
1. I don't think Eri's going to give up. Kobayashi's had plenty of chances to make her give up, but none of them have been taken up.
2. Harima rejecting or accepting Eri's confession seems to be very important to Eri. That Harima does not seem to appears the be the only thing right now that's holding Eri back in Chapter 227.
3. This seems to be what Eri's doing right now (putting feelings on hold), but I don't think that this is going to really be an option for Eri. Events happen beyond her control, after all, and Harima has a way of screwing up his confessions.
After so many chapters being spent developing primarily Eri's side of this relationship, I really think that it's up to Harima now to decide the outcome for these two.
Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you. - Friedrich Nietzsche