At about $1500, you'll get a good quality aluminum frame and either Shimano 105 or SRAM Apex drivetrain, both of which are also good quality. The choice of which brand to buy comes down to which brands are available in your area. The bikes in this price range will be about the same in quality and features, so when you check around, take note of which shop treats you best. Do they answer your questions respectfully, or treat you like you're as dumb as a box of rocks? Do they explain stuff or just roll their eyes? Do they work with you within your budget, or try to push you to buy a bike above your budget? When the bikes are as close as they are at this price point, shop by customer service. A good shop is better than a poor one, including when the poor shop is a little cheaper.

Saving money by buying a bike that's on sale but doesn't fit is a bad idea.

Another thing to check on is whether a basic fit is included, and how much after-purchase maintenance is included. The norm is that the fit is included as part of the purchase price, as is at least one tune up; some shops offer a year's worth.

Women-specific sizing is also available at this price point. It doesn't mean your girlfriend HAS TO get one, just that the option's there. Some women fit on the standard versions better than the women-specific versions.

Some folks have recommended buying online. IMO, it's a bad idea because the money saved is often eaten up by things that come included in the purchase price at an LBS (like fitting and tune ups), and if you have a warranty issue, it's much more of a hassle.

Best of luck on your search!