If you have enough financial support, why not drive her to Vegas. But this is a risky proposal once you bore her during 4-hour drive there. Above basis you drive 70mph for this 270miles trip. You may collect some Japanese love songs or her favorite singer album to play during the drive.
You may plan a one-day round trip. Depart at 10am then arrive Vegas 2pm. You can have lunch & window shopping at the outlet near Vegas. Suppose you arrive Vegas at 3~4pm, you may go coca-cola town & M&M shop to kill time until evening. Then it's time for show. Either "Le Reve" of Wynn hotel or "O" of Bellagio hotel. After show you can see whether she is happy or not, then you can identify if there's any chance for stay one night in Vegas or just drive home.
If you can cheer her up this whole day, not far for your success. On the contrary, you know the result if you fxxk up.