The McMillan stocks are pretty much standard dimensions in the grip and would be difficult to change. I think the walnut stock plan would work out better.
Sounds like you want to keep the original stock. If you can get a beat up one from your smith or someone here it could be shortened, thinned, trimmed, built up and ground down. She can try it out for a while and when it is good it is used as a pattern. Bondo automotive filler is a quick and easy way to raise a comb on a pattern, it is just ugly.

Mark
I have a CZ 550 in 9.3