The only advice I can give is buyer beware.
The more you know, the greater chance you have of getting somthing that works. Educate yourself on boots and boot fitting. It isnt hard. Alignment might start to get complicated...and actually resolving issues might take some skill...but dont let the scare you off from learning the basics, armed with the basics you will know alot more then most "boot fitters" out there. Trust me on this.
You should understand her foot width, and know the width of the boots you are buying. Not sure...ask, if they dont know. Leave. But dont just take their word for it.... "look" at the boot, narrow boots look narrower then wide boots....because they are! Double check on the net the boot dimensions too...again alot of "boot fitters" dont know and just make numbers up. Dont think there is big difference from a 98mm last vs 102 last? There is a huge difference.
Take the liner out and look at the heel pocket, is it wide? Narrow? What do you need..ie does she have a wide or narrow heel?
Do your own shell fit for lenght...again this isnt hard to do.
Does her heel lift when she flexes forward?
Can her foot twist or rotate up in the boot?
(these things can be fixed....but you need to understand if these issues exist first)
Look at the instep hieght, is it high, low, what does she have?
After looking at a few boots it wont be hard for you to start noticing the differences.
Comor has lifted their game substantially (well the Whistler shop did anyway) the Vancouver shop was absoluttley clueless. I overheard them once tell a customer trying on boots that it was normal for her heel to move around 3/4"-1"! But if they know have the 4th ave snow cover guys that is a good thing, those guys did know their stuff. The Snowcovers in Van is worth a try too.
Snowcovers in Whistler has definatley lost the bulk (all?) of its knowledable staff.
I am not suggesting you dont need someone who knows....but if you do some basic research yourself, you can weed out pretty easily who knows, and who doesnt. Most dont.
When in doubt on sizes, pick the smaller pair. Almost all beginners end up with boots 2 sizes too big.
Take some measurments and photos and post in the "Ask the Boot Guys"...they should be able to point you in the right direction also.
Final point fittting beginners is one of the hardest boots to fit. Experts and racers are easy. Why? Because experts know what the boot should feel like, they can say, it is too this or too that...beginners have no reference.