Make the cost of ingredients (unguents, salt, canopic jars etc) cost the same as a scroll of create undead from a 15th level cleric.
Throw in a few skill checks of Profession:Embalmer.
If the scroll is above her level in some way, she'd need a spellcraft check to cast. So something similar for a profession check. But since you're substituting a spellcraft check, witha profession:embalmer, you should probably make the check a little lower than the spell craft check would be, but have several of them.

Failure at different points uses up different amounts of the ingredients.