I am just going to put this out there.
Domestic dogs are not wolves. There is research about it.
Domestic dogs live in families.
Ie: You are Mummy, OH is Daddy and the dogs are the kids. They do not have a pecking order, except that YOU are in charge, you control resources etc. Neither dog will be dominant over the other.
Yes you *might* have spats. But a healthy "spat" would be your older dog, telling your younger dog off by growling maybe a quick snap but nothing more, if your older dog goes any further then that, well then you need to break it up.
Pups have what we call a puppy license until about 6 months old, prior to 6 months you older dog will probably let the pup get away with loads and then all of a sudden after 6 months will start telling pup off for things. So keep on eye on that.
Nala telling the pup off though is not a dominant thing, it is a manners thing, and a well mannered older dog is a great example for a pup and will help you pull a pup into line and teach it manners when around other dogs.