I want to show my girlfriend I appreciate her?

So this past week I've been working overtime at work. I've been doing 12 hour days all week. I'd get off at 3am and come home and the house would be clean and she would have some good food waiting for me. So I was thinking, I want to take her to a fancy dinner tonight. Would this be a good way to show her I appreciate what she did? If it's not, what are your ideas?