It's confusing, this. It contradicts everything her memories tell her, that humans are dangerous beings, things that are out to destroy her and her kin.
Her first impressions are a bit of a mix of that.
But Kyle is there, and her memories tell her that he is good as well, though she couldn't tell you where the memories came from. There was just something deep inside of her telling her to trust this man, no matter what.
So Sunny did.
And it was scary, because humans were out to kill them, and they could easily succeed.
But her instincts were telling her to trust Kyle, so she would.