In the given scenario above, evaluate and discuss whether a third party should intervene. Explain your response. Mediation calls for an objective third party to provide a reasonable perspective, a controlling influence and a sense of compromise to an otherwise rancorous situation. With respect to conflict management, it is incumbent upon the mediator to help conflicting parties come to some level of mutual understanding as well as to arm them with the tools to independently manage conflict more effectively in the future. Certainly, this is a role which would be most welcome in the conflict between Leanne and her mother. Leanne's older sister appears most suited to serve as a conflict mediator here and, in fact, both Leanne and the mother are prone to seeking her ear when venting about one another.

In this case, the best cause for the sister to intervene and to serve as a mediator is the...

Such is to say that both Leanne and the mother have coherent points to make to one another. However, their conflict has reached an intensity that prevents rational discourse. Therefore, without objective mediation, they are unable to express their needs and concerns to one another. The sister has an opportunity here to provide them with a forum to express these feelings, such that Leanne might continue to enjoy her privacy and that the mother might gain some piece of mind in knowing her daughter's activities aren't compromising her safety. Additionally, the sister has an opportunity to help both mother and sister develop effective methods for managing disagreements in the future before they approach the proportions of the current conflict tension.
Works Cited:

Abigail, R.A. & Cahn, D.D. (2011). Managing Conflict Through Communication, 4th Edition. Pearson.