I knew it I knew Henry would end up sacrificing himself! That has to do it!
Hmm, I don’t think the sacrifice itself is what will make Emma believe. Knowing her, Emma would think Regina was attempting to poison her, but in a mundane way, not a magical one. I think what will make Emma believe is if nothing works to save Henry but he wakes up when she kisses him – unless someone interferes with that.
Expect the unexpected, Accept the unaccepted.
You that’s where this is going kiss from Emma, but now I’m thinking that breaking that sleeping curse will also bring back the towns memories?