Who hacks a Girafarig? Anyway:
i. I don't know if Entree Forest is the meeting place for Dream World Pokemon, so maybe check against a Dream World Pokemon of your own.
ii. in BW, the chances of passing down a hidden ability from a fem. parent is 60%; in B2W2, it is 80%. It is still not 100% sure that the offspring has the hidden ability.
iii. if you've bred the Pokemon with a Ditto, it will not result in hidden ability in the offspring, even if the Pokemon is female and has its hidden ability.
If the Pokemon isn't hacked, the Pokemon you've bred with isn't a Ditto, then you've just been unlucky.