I think you've gotten some good advice from jlspink22. If you can return those Riedells I would, but only after the meeting with the fitter, if you can wait.
And for the record, no-body likes new skates. They're stiff, they hurt, and they don't know the steps. With kids it's even trickier though, because you don't know if the skates hurt because they don't fit right, or simply because they're new. Heat molding definitely would help with that, but I don't think it's magic. Of course a 7-year old is in a better position to communicate fit issues than say, my 4 year old.
Also for the record, it sounds like your daughter is doing just fine. Her troubles may be skate-related, but they do sound like just old-fashioned learning, too. While better equipment may help, it won't be magic. If her skates still fit, and offer her the support she needs, there's no reason to get new ones. The fitter will be able to help you decide, and if they're a good fitter, they won't try to sell you something you don't need. This is also a good chance for you to get a feel for the local skate resources. If you have more than one skate shop in your area, it's worth it to check them all out; you can just walk in and talk to them you don't necessarily have to do the full on fitting. Ideally you want a fitter who works with several brands of skates since all the brands fit a bit differently, and can do modifications to the boot beyond heat molding, this will mostly involve punching out. They'll also probably be your blade sharpener, too, unless you're lucky enough to have a good one of them in your rink! So it's good to work with someone you trust, since this will be a relationship that will last as long as your daughter skates (and you, too once you get bitten by the skating bug!).
If your daughter does turn out to have a Riedell foot, the pain around her ankle could be because they're too tight around the ankle bone (among other things....), the easy fix for that is heat molding with an additional punch-out, if necessary. Like jlspink22 said, maybe the fitter can do the modifications to those boots and you'll be good to go.
In terms of blades, unless you have pre-mounted blades on PVC soles, you can put any blade on any boot. So you're not limited in blade choice by the boots you have. I think you said she's on a Mark VI? It's a fine beginner blade. Ultima, MK and Wilson all make very good blades, as do Riedell (the Eclipse). You can choose from any of those marks and be just fine. I think most people go into an MK Professional or a Wilson Coronation Ace (or the Ultima or Eclipes equivalent) at your daughter's level, or a bit higher. Discuss it with her coach. Like with new boots, a higher level blade won't be magic, but it could help with some things. Get them used if you can, too! But be sure to have someone who knows what they're looking at evaluate the blade (with you, so you can learn), to make sure the spin rocker is still there and that there's plenty of sharpening life left.
Good luck with the fitter, and let us know how it goes!