
Sorry to sound negative, but it sounds to me as though the boots just don't fit. I had blisters with some ill-fitting boots when I did a long walk last summer: it was a nightmare, as I've not really had blisters when walking for about 15 years! Anyway, when I got back I bought 2 (different) new pairs of boots with Superfeet Custom insoles, and the insoles hold my feet in place. I've had no problem at all.
Something is definitely wrong in your g/friend's boots: assuming the Superfeets were properly fitted, I think it must be the boots. Did she buy them at the same time as the insoles? If not, that might be the problem. If she did, though, I'd be thinking of going back to the shop for a new pair of boots and/or insoles...