The facial template she's based on is broken, so her children will all seem to resemble another template (it was the elf one for me, but for some it is Face 2) until they become adults. So, as you said, they may look fine, but they change dramatically when they reach adulthood, and they don't resemble Jessica at all (until they become adults, only to switch back as an elder).

Meetme2theriver and I have been working on recreating the sims with broken templates and replacing them in the game with SimPE. Here's my original post about it: http://strange-tomato.livejournal.com/258526.html