So I think Ava will return after three days because, you know, ~jesus symbolism~ but obviously for her it will have been years and also she won’t be in a position to reunite with everyone right away.
Because, as we know, the only way out from the other realm is the arc — though tbh I don’t think that’s how Michael got back or his mom would have seen him, but it’s possible he came back another way bc he had Reya’s blessing and she sent him back to defeat Adriel, meanwhile why would Reya let Ava leave when her halo is finally back where it belongs?
So maybe the only way through for Ava is the arc, she comes through that way but arctech is still swarming with ex-adriel fanatics and so it doesn’t go well for her and that’s why she stays separated from the others for a while. She could come through with the halo depleted, easy pickings for them, and they do have divinium so they could use it to contain her in some way. Just thinking…