In the LoT incident, there wasn't a solution apparent at the time that didn't involve killing Kei to destroy the LoT, which is why Bell was willing to opt for the double suicide approach. What it all comes down to is I really don't think she'd put her happiness over the welfare of the entire world. In the OVA, her presence aside from doing damage to the world in general was endangering Kei. The concept of reformatting into a different life form hadn't been introduced yet even in the Manga, I don't think, (My chronology may be off.) so the solution wasn't there. The author hadn't created it yet. Plus, the OVA is kind of its own cannon, really. Just as the movie is. So, in the OVA, the best solution she could see for Kei's well-being was to step out of his life and make him forget her. She was willing to accept that pain for his good.
15-Jan-2008