You cannot keep the memory of a sim you are moving to another neighborhood since the Sims she has memory related with are not part of that new hood. It would mess the game up.
Indeed face templates only works on newly created sims.
There is no way to make the face remplacements works on your already created sims. Moving your sim to another hood won't change her dna at all.
The only way I know you can alter the look of an already created sims is by following this tutorial:
Tutorial-Giving your in-game sims a permanent make-over