My partner is blind from birth and she has been using PCs for the past 15+ years. First of all, disregard that awful Best-Buy salesperson. Any blind user is perfectly capable of using a laptop or desktop without much modification. So please don't let that salesperson's ignorance discourage your daughter.
All of my partner's equipment has been PC-based (as opposed to Mac). To make a regular desktop/laptop accessible for a blind user, the idea is relatively simple: one installs an intermediate software layer which reads out the text that is displayed on screen, this software is commonly called a screenreader. Usually, screenreaders also provide functionality for navigating the Operating System (OS) environment without a mouse.
Historically, the "benchmark" screenreading software has been JAWS for Windows from Freedom Scientific. This software provides a somewhat stable environment and it might be a good starting point for your daughter. Lately, we've been looking at other screenreaders like Window-Eyes from GW Micro, which claim to be more stable. JAWS does crash and it is particularly frustrating for a blind user to have its screanreader stop speaking. Also, we notice that most "pro" users have two or three screenreaders installed in their PCs in case any one of them crashes. Additionally, there are some open-source solutions available like NVDA, which you should also check out.
In the Mac realm, the situation is more limited and the number of available options are more restricted. We've heard good things about Mac solutions, but haven't had first hand experience with them. (We also prefer to have more options at a lower price, so Mac can wait).
About which laptop/desktop to buy, we can give you some pointers:
1. Portability. Since this laptop is specially geared for your daughter, she will want to take it everywhere from school to her bedroom.
2. Video/Screen. Obviously, you don't need a big state-of-the-art video card (so save your money on this). If you can get a laptop which completely dims the screen, this is even better. Your daughter will be able to extend battery run-time by switching the monitor to completely black.
3. External volume knob. This is a feature which has been tending to disappear, but some laptop models have an external volume knob (as opposed to digital controls or OS based controls) which is easier to operate by touch.
4. Touchpad. We would suggest a touchpad which can be deactivated with an external key. Tapping on a touchpad is annoying for my partner, but at the same time, it is more convenient to activate the touchpad's full set of features when I provide sighted assistance.
5. Memory, Processor, etc. As with any other computer: more memory is better. A faster processor is better. Get a something with decent audio capabilities.
Braille displays are a touchy subject. Braille is defintely a plus in a blind person's life, but braille displays are expensive, delicate and a bit clumsy. Screenreaders allow the full operation of the PC without the need for a display of this kind. If you have the money, go for it. My partner does not use one.
One other gadget you might want to look at is Eye-Pal from AbiSee. This is the best scanning software/hardware combination we have seen so far.
Finally, let your daughter experiment with the laptop. In our opinion this is the best way to learn how to work with it. Worst comes to worst, you can always have all software (including windows) reinstalled.
Good luck with everything!