Try writing a version of this that does not mention "Megan". Your end goal really is to get training so ask for what you want and list how it will make you a better employee.

This letter may make them focus on the wrong thing and see you as the problem. If favoritism continues you can address this at a later date. I worry that the favoritism thing although most likely true, doesn't serve you well to bring it up.

It may work out better for you to just ask for what you want.