spazboy's page

Of course for two more levels ECL 15 you could give her fiendish or celestial template, that would boost here resistances to a lot of types of attacks, but you wouldn't gain any extra hit dice.

There's something crucial being neglected here and that is Effective Class Level is not solely the level adjustment, it's level adjustment plus number of hit dice. A nymph has level adjustment +7 and 6 hit dice. That means a nymph would be equal to a level 13 character, not 7. The stats and abilities for a nymph greatly outweigh that of 7th level character, the trade off is that you have only 6 hit dice for a 13th level character.