I really think she’s going to bounce back REASONABLY quickly when he dies. Because she’s already experienced it twice, she knows what it feels like. And the last time she lost him she kissed Hook not long after. That’s against the show’s canon for TL, as you guys have said MANY times before.
I think Emma will be fine too. If the death is truly story driven and Emma’s already said that she wished that Neal “died” the first time, that was a trick because it’ll be easier for her to move on — this time because it is a real death, because she’s already experienced loss with him, it will be easier. She’ll probably still grieve, that’s to be expected but it’ll be easier this time.