Is it normal for this to be so awkward?

I have started talking to my half sister again after ten years. She's almost 25, I'm almost 14. She never had anything do with my father, she was raised by another dad. Anyways, we reconnected via facebook a year ago and it's super awkward. We talk sometimes, but it almost like I'm afraid of her. She shares a lot of personal information with me, but I can never open up to her. My Dad doesn't particularly want us to be talking, but I still do. I'm afraid of what she thinks of me. She has a small family, and sometimes I feel like I'm just wasting her time. When we email, sometimes I get nervous about emailing her back.

Is this normal?

Don't get me wrong, I like her, and admire her and everything, it's just super awkward.