NHF – new heroes for Heroes V 3.1.

You could give her a necromancer amulet instead, if that's not possible. And increase all stats by 2, for example.
I wouldn't say it's an overly powerful special ability. 10% necromancy and -3 (3.5) to morale and luck at level 20 is not that much...

To achieve such results, people take the 21st ability and spend one turn, but here you don't need to do anything, take what you want, and you also get a bonus to leveling up (although she still won't have enough energy). It's the same as giving an elf +1% chance to trigger luck per level.