Hello and welcome.

My 9 year old female Akita (Sheba) is that way with our
little female terrier, Pepper.

Sheba moved up to top dog after our Alpha little Terrier past away. Our Alpha Terrier was always putting Sheba in her
place till the day she past away.
Now Sheba is getting even and treats Pepper like our Old Terrier treated her.
I always repremand Sheba when she does this, to remind
her I am the boss and not her. But to be honest
she still growls at Pepper, when Pepper approaches
while we are next to Sheba.

So other than trying to reinforce yourself as Boss,
taking toys and food away, and basic obedience
with your dog, that's about all I can think of.
Oh and one thing I stopped doing, is when Sheba
comes up asking me for attention, (when Pepper is around)
I will ignore her and only pet her when I decide to.

P.S. I am still working on this problem too.