Her attack stat is high so I’d just go that route, especially since she’ll almost certainly be on your titan team. I know Scarecrow has also said offensive Fighters should pour on attack so it’s more devastating if they revive and fire.
That said, I didn’t fully spec her out and would do that before I decided. My guess is it’ll be like Jackal; even going full defense / hp it was obvious he’s be upgraded, at best, from very fragile to regular fragile. So I felt going full attack and hoping he survives through Evade a bit longer was the best course. I’d guess Elena could maybe go from fragile to whatever is slightly better than fragile but still well shy of robust. Attack, let the revive work from time to time.