There is no such thing as a "best" knife set. It all depends on the person using them. Take your Mom to the shop and have try out the knives. She needs to hold them in her hand and actually chop stuff to get a feel for how the grip works for her and the level of fatigue she gets over time. Some people feel more stable with a squared off handle, some prefer the rounded handle.

I also think that knife sets are not particularly useful-- lots of things that she will never use. Get a good chef's knife (length depends on the person-- 8-10 inches is standard) or santoku (depends on what feels best in her hand), a paring knife, and a slicer. Add a cheap bread knife if she slices a lot of bread (cheap because they're difficult to sharpen-- it's easier to get a new one every couple of years). If she hacks a lot of carcasses into pieces, consider a cleaver, but get it in Chinatown. If you think she'll use it, get a sharpening steel- or a Chef's Choice grinder if you think she won't use a steel.