Shelly and Brooke can be made to reconcile using the skills of the 4ds.
Explanation:
Using the 4Ds of a Difficult Conversation (Define, Defuse, Discuss, and Decide) is paramount in this discussion.
The real reason is that they are not able to deal with the inclusion of Evans in their dynamic.
So they must acknowledge this fact at first and it would come as the process of being able to define.
Then they must be able to diffuse tension by acknowledging that the presence of Evans is not what is the core of the problem to diffuse the situation.
Then they will discuss what they can do best to curb the communication gap.
Then finally they will decide on the course to take