OK...I could have worded it better than "if money is not an issue"

If you can't find a tall mixte (a quick ebay search showed 48 and 49 cm....good for east hill not so good for you fiance) you might try getting an older non suspension moutain bike. The can be found used pretty easily and reasonably priced. Mountain bikes tend to have more room from the top tube. Put smooth tires on and you have a not bad first ride. If you really want to get clearance, look for a small frame and put a taller seat post and stem on. And another option is to look for a "compact geometry" ie non level top tube road bike.....not as much clearance as a mixte but more than a classic frame...

good luck