It may be important, in this case, to retrain your primarina on two levels.
First, you’ll need to remind your primarina that she is only one half of a team and that she needs to work with your dewgong in order to succeed. You may wish to engage in team building exercises (practice outside of anything directly related to your water show, for example—or in other words, have the two work together around your home or on other projects) in order to strengthen their bond. Likewise, teach your primarina effective ways to offer constructive criticism. Whenever she speaks to her teammate(s) harshly, tell her firmly that this isn’t acceptable behavior. However, if she speaks to her teammates gently and offers advice on how to improve (demonstrations, for example, or communication that seems to please your dewgong), give her a reward of some sort and thank her for her contribution. Eventually, you should be able to correct that behavior and encourage her to support her teammates in more constructive ways.
Second, of course, you’ll also want to remind your primarina that you’re both her trainer and dewgong’s. Tell her that the routine she’s going through is essentially one you’ve created for her and that you accept that it could be weak at points. Work with your primarina and your dewgong to hear their concerns and try to find a compromise that will work for the both of them. You are, after all, their team leader, and a team works together most effectively when it has a strong leader to guide it.
Best of luck, anonymous!