The market is pretty much "you get what you pay for."
In the under $300 range, the Kitchen Aid 5 qts are pretty much as good as it gets. If she's serious about baking at home, they are good units but a little undersized and underpowered.
In the $300 to $400 range, there are two Kitchen Aid 6 qts, the two Cuisinarts, the DeLonghi, and the Viking. These are all very competitive with one another.
I think the Viking might have a slightly weaker review and customer feedback record.
The DeLonghi doesn't actually have much of a rep one way or the other, but it's been a big favorite forever in England and the Empire under the Kenmore (no relation to Sears) name.
Outside of the usual individual customer complaints, I haven't heard anything bad about the Cuisinarts. But I haven't heard anyone who knows very much say they're any better than the Kitchen Aids either.
One further step in price will land you a Bosch, or a Hamilton Beach Commercial.
With the HB, "commerical" is very much an operative word -- even though it's more of a semi-pro than an actual pro. Don't buy the under $200 home model. It's not enough machine for a serious baker -- even one who doesn't do much bread. I've heard that the HB can be a little iffy on very small amounts -- say meringe from one egg white. Otherwise they're supposed to be very powerful and quite good.
The Bosch is a good machine -- but if you buy one, for heaven's sake buy the metal bowl. The plastic bowl deforms with heavy loads. It works, but it looks as weird as snake wearing suspenders. Creepy. One of the nice things about the Bosch is that you can get a pretty good mixer attachment for a reasonable price. If you don't want a mixer attachment ... you still get the integrated mixer tower. More weirdness.
Top priced home unit is the Electrolux; if what you want to do is mix a lot of bread dough, it's probably the best choice. Does everything well. Expensive though, pricey attachments too. Personally, I wouldn't buy one with my money. But then, I've gone back to mixing and kneading bread by hand not just because I had to, but because I'm happy to exchange the extra dozen minutes for the extra quality.
A final word about Kitchen Aid: You'll no doubt get a lot of "stay away," advice based on the fall off in quality since Hobart spun KA off to Westinghouse. The first new machines introduced after the spin off had plastic in various places it shouldn't be -- notably the gear housings. These machines were indeed bad news, and failed like crazy. Worse, KA did not do a good job of supporting their customers.
Happily, that's in the past. KA redesigned the machines so that everything which should be metal is metal and improved their customer support as well (not that it's perfect). But, the internet loves bad news and doesn't forgive easily. No doubt, you'll hear the old truths repeated as if they still had validity. As Antony observed, "The evil that appliances do do lives after them, the good is oft interred with their bones."
In the interests of disclosure. I was an owner of one of the early, plastic wonders which I bought to replace one of the older last-forever models that went with my ex. The new one broke; got fixed (not cheap); broke again; and KA no longer makes the replacement parts -- so I'm SOL.
When I do replace the machine, I'm pretty much stuck with KA so as not to render all of my KA attachments redundant. That doesn't make me unhappy though, as the old problems appear to be gone. Attachments aside? Probably another KA. I'm just not in a hurry.
As to which e-tailer has the best price for a given model -- you'll have to do your own research.
Hope this helps,