I'm 5' 1" and I am fine on off the shelf bikes. Unless you have an unusually LONG torso and short legs, there are small bikes out there. And felt does make a bike small enough for you. I know, I sell them.
Since I am so short I help a lot of ladies of my "stature" get on bikes. Their smallest bike is actually pretty darn small. In fact I have put a few young girls on them. We have a large contingent of kids who "tri" out here, and mom and dad are always itching to get them on a road bike asap.
Unless you really want to spend the cash, there is no need to go custom.
I'm glad your getting a pro fit. Are they using a size cycle, measuring, or both?
If it's a "pro" fit you should be in good hands. BUt, If you have any questions I'd be glad to help you. I can't sell you a bike. But it's important that you get the right fit.
- This coming from the girl who KNOWS she's a 44-46 depending on geometry, but wanted the Felt garmin team bike SO BAD that she ordered the 47 (smallest size they make of that model) anyway... Yeah, it didn't fit..

edit to add: and yes their small bikes do have 650 wheels. They had a Junior roadie last year that had 24 inch wheels. Pretty cool.