I need some ideas/suggestions for a Bridal Shoot

I'm going to be doing a bridal shoot for some friends in Chicago in a few weeks. They live in the city and have a great view of the skyline from the top deck of their apt. complex.

We're trying to figure out how to pull off a shot with her in her gown, and the skyline as the backdrop....AT Night! Not sure how to pull that off with lighting so that it balances out...

Would it look to 'fake' if we took two seperate shots at different times and then layered them?

Ideas...suggestions?

Too much trouble in PP to combind a daylight subject and night scene. Try some test shots of metering for the background skyline with higher iso and longer shutter speed, and use flash to light foreground subject.