Pinning her as in grabbing her and dominating her?? That shouldn't work the way you want

you're teaching her that pinning is a game to perform on smaller buddies. I think the corections should be implied when she so much as looks at the cats. Not in a negative way but you need to teach her that the cats are not toys. To do this, find a correction sound that is consistant and works.. A hiss, a "spiss" (like you would to get a cat off the counter), clap your hands, snap your fingers. . Whatever it is, couple it with "No". I heard that if you say , "Morgan, no" she will hear her name and use it as a positive reinforcement ignoring the "no". So just say "no" or "lay off" or "leave it" (keep it short) and when she learns to back off say "Morgan Good Girl!!!" and make her the queen again! The second she gears her energy at the cats correct her again.
I think something like this can be enforced without physical enforcement. How old is she now?? Boxers are very high energy dogs (as you know

) and maybe take her for a run first before training her. Remove the cats during training as they are quite obviously a distraction!
I hope this helped!