How do you think the Snow Queen knows Emma?

So Gold said "Did Miss Swan recognise you?" so they've obviously met before.

There was a lot of theories of Zelena being alive and how she could still be alive, but in the body of someone else. Could be that.

Other than that I don't have a clue. Unless it's to when Emma was in foster care, but she wouldn't remember her so that would be a stupid question. Plus she was trapped in that urn for a long time.