But also not nearly as effective.
she has a fleet. Revan's is much, MUCH bigger.
Nihilus' fleet effectively destroyed the colony of Katarr, which WAS defended by multiple hammerhead cruisers and was only destroyed by the actions of the Mandalorians and the Jedi Exile sabotaging it.
EDIT: And what army she does have is not nearly enough to wage a full out war.
Nihillius's fleet lasted a grand total of one battle. And they lost it. Against the Republic.