Why? Well I think there is something about the sword that makes her teammates forbid her to open it? Maybe it requires huge magic portion? Who knows? Or maybe she’s too exhausted to use it? Or maybe the sword will cost her own life if she open it.
2. Milliana’s blood
Minerva transport Milliana and exchanged it with Erza? Her teammates forbid her because suddenly Milliana’s there.
3. Erza’s blood
This is maybe 95% impossible due to Jellal’s face that seems calm and the Fairy Tail’s members shocking face is not too dramatic for a member’s death (kinda confusing, i know). AND THERE’S NO WAY THE MAIN CHARACTERS WILL DIE! THERE I SAID IT!….