Hmm puppy playing too hard with one child ignores other

So alone with out puppy Forrest who is about 4 months old now.

We also have 2 children, my niece Loralei who is 4 and we have perminate custody of and our daughter Tori who will be 3 in december.

Forrest will completely ignore Tori even when she's yanking on his tale or pulling on his ears. They often will be seen sitting on the floor next to each other watching TV, or when she's just sitting there playing with her books he will lay down next to her and nap.

Now Loralei on the other hand. He can not seem to leave her alone if they are in the same room together and my wife or I are not there.

He will get on the couch with her and start pouncing on her and mouthing her. He's never bit her to leave marks or anything like that. But it gets to her at first she will be fine (I've setup a camera and watched it happen.), she will be sitting there and actually get him to come to her and start playing with him. Then he gets too rough with her.

I'm thinking it's almost more her then the dog. Cause we had the same issue with our previous dog before we had to put him down due to seizures (our 2 year old German Shepard), he would chase her around the house and mouth her arms/legs and knock her down. But would completely ignore Tori...

Any ideas on how to get this to stop? I try my best to tell Loralei to leave him alone but being a 4 year old and the way she was treated/brought up in her previous house/lifestyle she doesn't listen very well.

I try my best to also discipline Forrest when I catch him also.