Tell how trip is funded or fib?

1) Can you find a way to describe it that's honest but doesn't make her feel too indebted to you, like "Thanks to my work I'm able to get us these reservations that are totally affordable for me, so please don't worry about paying for anything, I am delighted to treat you and spending this special time with you is exactly the birthday present I want." (She doesn't have to know that you just mean that your work is where you earned the money that makes it affordable for you.)

2) Aside from the trip, you should be honest with her in general about how rich you are.