Dude, you wasted my time reading your post by placing the word "married" towards the end.....!!!
Ok, what lens do you have? Wide angle? 50mm? Telephoto?
Well, obviously you got to pick a good place. She's married right? May be have her hubbie around just in case.
I'd also bring a ladder with you. You can then shoot from higher angles, say with an ultra wide angle down wards on her and the car ( sexy girl laying on the car drool drool...). Don't be afraid to use the flash to try some unconventional shots. Just remember to be aware of how you want the shoot to be after post processing, then plan backwards.
Also, consider some chase shots (you in a car shooting her driving her car), panning shots... whatever that is in motion.
Or, you may want to bring a fan to blow at her for some special effects! No kidding, it can be cool. Not to spoil your plan, but I can imagine purposely blowing the fan at her back wards while she's driving forward, creates a conversation piece.
Sh*t, I WANT TO BE THERE!!!
Yes now you've got an excuse to browse hot girls+car photos all night long.
I did notice while browsing through shots last night that a ladder might be a good idea. I'll look into borrowing my brother's ladder. Worst come to worst, I can stand on my truck.
I've got a Tamron 28-80mm that replace my old Canon lens that crapped out, and a Canon EFIII 75-300mm telephoto. Not the best glass, I know, but I just can't justify spending money on something I'm not that great at. It's not like I do these shoots a lot. For me, what I have works. Personally, I think I need to hone my skills more before dropping major coin on better equipment. Skills make good pictures, not equipment, IMO.
She IS married, but her husband is in FL right now, as he's military. Like I said, he's a good friend, and he's fully aware of what's going on. It's simply not an issue.
I'm not sure I could do chase shots. The roads are pretty open down there, but honestly, I'm not comfortable taking photos while I'm driving.

I'd use a fan and "fake" it, but I don' thave anywhere to plug the fan in. I'll keep that in mind for other shoots though, if it comes up.
As far as shooting the car, check out this web site, it's all about shooting cars. Tips, techniques, ect., good luck and post some stuff up afterwords.
Car Photography Tutorials - A CHRONOLOGICAL OVERVIEW OF ALL OUR TUTORIALS
Thanks for the link. I'll browse through that tonight.
FWIW, here's a couple "test shots" I did with my truck a few weeks ago, to see if I could find a good angle.
No shots near the old warehouse buildings though. Sorry. Not sure if I'll use this area down by the water or not. I kinda feel like the ships are a little overwhelming.