Hi Sarah, congratulations on your new puppy! I have two females that are 3 and 5; they've lived together for 1.5 years.
When they met, the younger one wanted to assert herself as the dominant one, and the older one acquiesced…. they've determined their roles, so there really isn't an issue here.
The younger one, Lola, is a "licker" and often initiates playtime. If the older one doesn't want to play, she will snark at Lola, who then decides that the new game is to clean Becca's ears. 🙂
I think the guideline to introduce them in a neutral place is a good one until you know how they will interact when your puppy goes to visit Bananas.
Hugs and roos!
Patty