Couple things from someone with odd shaped feet that hikes/climbs a ton:
-Boot fitment is the most important aspect to buying boots, not brand. Buy what fits and will do the job you are looking for.
-Fit the boot to your foot. front end sliding around, you can get thicker insoles or shims to put under the insole to reduce volume. If the heal is getting blisters by rubbing on the heal pocket of the boot as it curves forward, lower the foot in the boot by having an insole thats thinner under the heal.
hopefully she doesn't have Haglunds deformity, it makes boot fitment a nightmare.
I have enough foot issues I make my own orthotics now, its a pain but cheaper and better than podiatrist made ones.