1. Bike fitting is extremely complex. You could talk to 3 or 4 fitters and get totally different answers which would be compounded by the way different bicycle manufacturers measure their own frames.
Start by going to wrenchscience.com. Register, and goto their bike fit calculator. You may also want to try searching for the "Lemond fit system" or read this webpage:
http://www.coloradocyclist.com/bikefitAlso note that when they're referring to inseam and such, its not your pants inseam, but your seat inseam. You'll need to apply some pressure to your "sit bones" to get this accurately.
2. Once fit is determined, you need to come up with 2 things.
A. What is your budget?
B. What do you want to use the bike for?
Since she most likely is looking for fitness at this stage, you may be thinking... I can just get something that accomplishes that. I would caution against this because there's a good chance everything will become obsolete (think PC type of obsolete). My recommendations are multifaceted.
First, no matter what, buy the bicycle for the frame. Components, seats, tires, wheels, anything can be changed for relatively low cost. The frame cannot.
Of the frame materials that you'll be looking at:
Steel, Aluminum, Carbon.
Steel is often touted as "soft and forgiving", Aluminum is "very stiff" and Carbon is "very stiff, but absorbing and light". Sheldon Brown has a great article about why this isn't actually the case at all:
http://www.sheldonbrown.com/frame-materials.htmlYou can also find mixes (typically aluminum and carbon) so as to market the frame as stiff, light and comfortable. My recommendation might be to suggest an aluminum frame if for no other reason than...
With Carbon, if it gets banged around AT ALL, it has to be gone over with a fine toothed comb. It is EXTREMELY strong, but if it falls over, if it gets bashed into, etc. etc. etc. it can become structurally compromised. Similarly, aluminum if dented can become the same way (think standing on a pop can and tapping the side (watch ur fingers kids)). Steel frames are nice, but they rust and require more maintenance, as well as being a little more rare.
All of that said.
3. Component packages.
Generally, I used to advise my customers of a couple things. Many people would often look long and hard at the entry level bicycles, with components that are typically topping out at the Shimano Sora level (goto shimano, campagnolo, or srams website to see their hierarchy). If someone is getting into a road bike, especially for fitness, its important that they WANT to ride it. That comes with having a bicycle with mechanical components that actually work. Sora and less will work just fine, but they are less reliable overall, and may require more adjusting, and offer less crisp operation over time. NOTHING is more frustrating than riding along and shifting gears and hearing the chain grinding away as it struggles to shift.
I'd suggest something in the Shimano Tiagra or 105 level. This will also keep you out of the 8-speed bikes that are on the lower end (10 speed is the norm currently). These components will offer essentially similar internals to the high end stuff, without all the weight saving parts (similar functionality without the added cost of the carbon fiber and titanium bits etc.).
Also note that bicycle manufacturers will generally sell a bike with "scaled components" so for example, you may see a bike with a 105 rear derailleur but tiagra brifters (slang for brake and shift lever (since they're combined on road bikes)), and shimano 2200 brake sets. So be wary that seeing "Shimano 105" written somewhere on the bike doesn't mean that the entire component group is 105. You may want to search ebay for a full shimano 105 groupset or gruppo and see what they're going for... that may help you determine what a fair price for the bike you're looking at would be.
Many bicycles (even some at the 105 level) are sold without pedals. This is because many people already have a set of clipless pedals that they'll be putting on. But just keep that in mind.
Lastly, any good bicycle shop should do a fit for you right then and there. I'm not certain how they work this at SBS, but I doubt you'll be getting a fit like this at scheels. If the frame size fits, but the reach is a little weird, they should offer to swap out stems or handlebars to get the fit to be correct. THIS SHOULD NOT COST EXTRA, unless you're getting a part UPGRADE. Most of the local bike shops though have a relatively limited stock of parts for roadbikes and may have to order it, or not even offer this service, so I suppose you don't need to mark it as priority one.
One final note, if you're gf isn't riding with GOOD spandex bicycle shorts, get her some GOOD ones (maybe a jersey too). Road bike seats will NEVER be smooshy. Thats why we wear bike shorts. It may take her a little while (couple rides) to break in her sit bones, so she should expect soreness. After a little while of consistent riding, if the seat still isn't jiving with her, it's time to get her butt measured and get a new seat. AFAIK, they DO have the gel measurer at SBS.
If you have more questions or need more clarity, just post. If I'm not seeing them, PM me.
