As a foster child, I’m pretty sure Emma Swan is used to people moving on with their lives and forgetting about her the moment she stepped out of their lives because she didn’t belong there. Probably the reason why she keeps running away. 

It is no surprise that Emma is so vulnerable and therefore quite rude to Killian- he is one of the only persons, if not the only, who swore to her that not a day will go by that he wont think of her he has been the only one in her life to promise her “eternal” affections - love.

Plus, he is the one person who never managed to move on with his life after meeting her. The only person who moved oceans and realms to follow her, to find her.

He’s literally the one person in her life who couldn’t forget her, who couldn’t live on as if she had never been.

It is no surprise that she was so vulnerable with him after and therefore kind of rude. because nobody held his promise like Killian Jones did.

because nobody loves her the way he does