Thanks everyone. It seems the consensus is that chosing knives is something very personal, so I will wait until I can take my mother shopping in the US or Japan to get what she really wants. Perhaps I can still surprise her a bit if I pretend we are just looking when we go to the store, and then later purchase all the things she wants. Anyway I care more about making the right choice than about surprising her with a gift (and there are always other opportunities to do that!)

OT, but when in the US I will have to do some shopping for my own kitchen. Cookware from brands like Fissler is ridiculously expensive in Japan, and I don't even think All-Clad is sold here.