Hi,
fellow collie lover and tonk owner. I breed collie roughs and also have a lilac mink alter male tonk. WNCA Grand Ch Tonkfuru Uchi who is a very fat cat now.LOL
In regards to clipping Brandy, I find it hard to understand that a grooming salon, wouldn't have the necessary things to prevent a dog (any dog who has had enough ) from nipping.
I wouldn't recommend having her clipped, I take it that she is desexed, that changes a roughs coat to start with IMHO.
By having her clipped, her coat will grow back thicker, and probably harder to keep up with, since that seems to be the complaint. It won't make her cooler, a well groomed coat, breathes and acts as a insulation. So unless she is matted to the skin, I wouldn't have her clipped, and I would run as fast as I can if a grooming salon recommends it.