Married long time and not dating, but I'll play the game... lol
The problem you'd find, is that gold-diggers don't take any chances. Time is money. So unless you start opening your wallet wide to show her a good time, and do it quickly, there'll be no joy in Rep-Town.
Also, ladies motivated in that way have a keen and suspicious eye for reps. When I was working in the jewelry business it was extremely common for beautiful young women to show up at the store with gift diamonds they'd just received to ask us to "test" them to make sure they were gen. Some even went so far as to ask our gemologist to do a full certificate on them (presumably because resale was in the pieces future). I'll guarantee you that as good as watches are these days, they'd do the same if you gave one as a gift.
All that said? I'd go with a Patek. As "bait" its a watch thats widely known so your ho... um... target need not be a horologist to appreciate it. And be sure (this is the clincher) to treat that rep Patek like you don't care how much it cost. Because props are one thing, but what you do with them tells the story she wants to hear.
BTW, with your mind on this sort of thing, you might appreciate the movie - Priceless -a French romantic comedy with Audrey Tautou and Gad Elmaleh as a gold digger and a gigolo. Quite good - and there are watches in it!
;-)