I am new to this forum, and don't own a King Charles Cavalier. But my mom does and we really need some help.

My mom's dog, Maddie, is the sweetest Cavalier ever! She is a certified therapy dog and just loves every dog she meets. That is, until I brought my new Golden Retriever puppy over to visit. She barks and growls at him every time he gets close to her! We stayed over the holidays and thought that it would get better, but it seems to be getting worse

i don't live with my mom, but we like to visit a few times a week. I am puzzled on how to make this work?! Any suggestions or help would be greatly appreciated!