Answer:
currently, Jill has to pay 30% x $120,000 = $36,000 in corporate income taxes
then, she must pay 15% x ($120,000 - $36,000) = $12,600 in dividend taxes
so her net pay = $120,000 - $36,000 - $12,600 = $71,400
if she decides to be an employee of her corporation, then she would pay only $120,000 x 25% = $30,000 in personal income taxes
so her net pay = $120,000 - $30,000 = $90,000
This calculation does not consider any FICA or FUTA taxes since I'm not sure where Jill lives and if those taxes apply there.