Captain Swan: Protection

A mysterious girl appears claiming that Killian is in danger from the Snow Queen. She claims that she is from the future and that it's her job to protect Killian.
No one knows who this girl is, but Emma’s superpower tells her that the girl isn’t lying. However, Emma isn’t about to trust a teenage girl who's willing to go to extremes to protect her identity.

Who is the girl? Will Killian be safe? Why did this girl come back in time to save him?

Note: This is my version of season 4 and Marian didn’t come back. I’m more of a Captain Swan fan, but I love Outlaw Queen too, I just couldn’t bring Marian in. Hope you like it! I will be including some scenes from the show, but I’ll edit them to fit my purposes.