Is it normal to feel like this?

So I've been seeing this girl for almost 3 months. We're not bf/gf yet. It was her birthday this past weekend so I surprised her with a 'birthday cake with 'Frozen' plates and (her favorite animated movie). That was 3 days ago and I already miss her. I even sent her a text saying that I missed her.

Is it normal to miss someone that you've just seen only a few days before? Especially if they're not someone you've known for a long time?