They are equally cute. Depending on what the kitten looks like, and what breed of puppy it is.
But what if I get rejected and she ignores me?
I don't think you will get rejected. Sometimes, it's best just to tell the truth and see what comes from it. What if she doesn't reject you? Then you lost an opportunity.
Should I confess my feelings for her?
You should always confess your feelings for someone you like.
People in grade 9 that you find really nice and always happy?