*Trigger Warning*

This is tricky. I think the reason you're freaking-out is because she is more relaxed about the relationship than you are, and you can see that, and so it makes you have doubts. It doesn't mean she likes you less than you like her.

That said, it would drive me nuts not to know where someone else stood as well. Maybe you should do yourself a favor, and tell her about how you really feel. Try not to worry about rejection (easier said than done). I'm putting myself in your shoes, and I don't think I would be able to handle this day in, and day out. Just tell her! Let the truth be known!