[The 4 M]

Really feel for you and the situation your in, without knowing details like how long she's been with you? has this behaviour been there from day one or did it start some time later? and many more questions, if it was me in this situation I would start treat training... sit both dogs next to each other so they both have focus on the "treat" then starting with your boy give a treat and then her next, she will learn respect that he goes first, I do this with my 4 and make each do "trick" then "treat" in the order they came, Milo number 3 lol took a while to get the hang of it he thinks he should be first and stills struggles with the excitement of "me me me", its not easy having a pack and having a "it's all about me" dog in the mix is even more difficult its just showing her she can still get attention without the attitude, in a safe way for your boy and so your boy doesn't get pushed out, make her aware her behaviour does not pay. Hope the situation resolves and you can have a happy pack