If she knows dallas and you want to surprise her or show her something new, got to fort Worth, its a great city she probably hasn't explored. Uber to Fort Worth, go to ether the kimbel/MAMFW (2h), the botanical gardens (2-3h), the zoo (2-4), or the stockyards (30m-6h depending if you want to get your drink on), all of them are world class level experiences and not crazy expensive. Look for a "clasic legacy" restaurant in Fort Worth, something like Lonesome Dove (tho fuck tim love) or Grace tho honestly you know your gf better than me so just do some quick research and you'll find the right place to eat, plenty of options. End the night by walking around Sundance square and take her to Skat Lounge. Its my favorite jazz bar in texas, and one of my favorite bars. They do allow smoking indoors so if that's a deal breaker Thompson's Bookstore would be a great alternative, and its much more upscale and a speakeasy. Overall I would plan on spending 300 to 700$ depending on drinks and dinner and spend about 6 to 9 hours doing it. Bonus points for getting a hotel room in somewhere like the Ashton Hotel and that can run anywhere between 120 to 400$ a night depending on room and date. Idk your budget but 300$ on the low end for a crazy date is amazing.

I will also give my best date night tip in Fort Worth, ive held the secret for years and now I'll tell it. Go to Gus fried chicken on 7th pick up a bucket and some sides, then go next door, its a wine bar, they allow outside food, they also sell Dom Perignon at cost (around 200$) for some reason. Take your chicken and eat it with the champagne. It is one of, if not the best pairings in food an wine ever. If she loves food this will blow her mind.